When I first brought out the Jump Stop, there was widespread skepticism that the problem of chain derailment was something serious enough to warrant a hardware solution.  The prevailing unhelpful advice back then was just to keep fiddling with the front derailluer to find that perfect adjustment, and try to learn how to shift more carefully.  These days, there is broad recognition not only that derailments happen for many reasons completely unrelated to derailleur adjustment or shift technique, but also that a range of hardware solutions are needed to address the various types and causes.  There is no perfect guide, and for every guide that exists, there is another guide that does one or more things better.  This page reflects my views regarding many of the leading kinds of solutions in hopes it will help those searching for a guide to find a type that is well suited to their needs.

In my view, the best overall type of guide for preventing derailments are ring guides mounted directly to the crank.  These are unaffected by crank flex, they prevent both forward and reverse derailments, they need no adjustment, and they experience the least wear.  And on bikes with front derailleurs, pretty much the only outer guides available are ring guides.  The chief problems with them are that many cranks won't accept them, or the guides have to take the place of the outer chainring, and most bikes do not have sufficient room between the crank and the chainstay for an inner ring guide.  But for those who can run ring guides, makers of outer rings guides (also called rock rings, bash rings, and bash guards) include BBG, Blackspire, E-Thirteen, FSA, Gamut, Hope, MRP, Race Face, Salsa, Spot, Surly, Truvativ/Sram, and White Industries.  Makers of inner ring guides include Blackspire, Raidium, and the Ronniering.

When you can't mount a guide directly to the crank, the seat tube is the next-best, next-closest mounting point.  Guides in this category are broadly divided into inner guides, for preventing inward derailments only, and double plate guides, for preventing both inward and outward derailments on bikes that have only one chainring.

Among inner guides, probably the most ubiquitous offering is the Chain Watcher, from Third Eye.  This guide uses a worm-drive metal clamp (i.e. a hose clamp) to adjust to different seat tube sizes, and has a hollow plastic horn for guiding the chain.  At roughly half an ounce, this is one of the lightest guides on the market, and has low each cost.  But the guide horn is positioned late in the chain-engagement zone, and it is flexible, soft, and easily damaged, worn or simply pushed out of the way by a derailing chain--and then it tends to pop back into place to hinder efforts to rethread the chain, making it worse than useless in many instances.  Despite having had the greatest market pervasiveness of any guide in the U.S., I would say it provides the least protection and has the worst durability, which tends to defeat the advantage of low each cost if you have to replace it often.  If you absolutely must have a guide which can fit a range of seat tube sizes, or non-standard sizes, this guide can do that, but on every other count, I'm hard pressed to think of anything it does well.

Coming in at roughly 1/3 ounce, the Deda Elementi Dog Fang is even lighter than the Chain Watcher, comparable in price, and also has a plastic horn, but that's about where the similarity ends.  The Dog Fang comes in the three most common seat tube sizes, rather than using the one-size-fits-all metal clamp, and the horn is solid plastic, making it considerably stiffer than the Chain Watcher, but it has a very small guide area, so it really falls more into the category of chain catchers than chain guides.  (A chain catcher catches the chain when it derails, so that it doesn't fall into the crank spider and get snarled there.)  As a catcher, the Dog Fang is quite effective.  As a guide, it may have a smaller guide area than the Chain Watcher, but I would still rate it more effective than the Chain Watcher because the solid plastic horn has much less tendency to flex aside and let the chain past.  It's not unusual to find Asian imitators of the Dog Fang fitted as original equipment on bikes.

At about one ounce, the Jump Stop is a little heavier than any of the plastic guides.  It does use a fortified flexible plastic clamp (also in three sizes), to minimize risk of damage to the frame finish, but it covers the entire chain engagement zone with a long-wearing stainless steel guide plate, with a large feed ramp at the top, greatly reducing the possibility of the chain going over the top.  The each cost will often be a little higher than for the plastic guides, but in most cases, the Jump Stop will outlive the bike it is installed on, and in many cases, units have outlived a succession of bikes, so the long term cost compares favorably against any other guide on the market.

Coming in at roughly 2/3 of an ounce are the Cross Single and Cross Double Chain Catchers from K-Edge (for cyclocross bikes with one and two chainrings respectively).  Though K-Edge calls them catchers, I would call them chain guides proper.  These are the best of the units I've seen that compete directly with the Jump Stop, though they have clearly adopted a different design philosophy.  Their aluminum clamp is stronger than mine, but also more damaging to frame finishes.  They prefer thick but inherently soft aluminum as the guide material while I think thinner, but harder, stainless steel delivers a longer service life (I've never had a report of someone wearing out a Jump Stop guide plate--but my warranty would cover it even if that ever did happen).  K-Edge feel it is best to put all the guide force forward of the seat tube, very late in the chain engagement zone, and make the guide as rigid as possible.  I think it is best to start guiding the chain even before it reaches the chainring, and to have a mount which will give way in case something gets snagged in the chain.  I designed my unit to be flexible toward the front so that it can run close to the chainring, and yet flex aside briefly to accommodate reverse derailments, putting it in a good position to rethread the chain when forward pedaling resumes.  I don't know how well the K-Edge units can handle reverse derailments, but I suspect the chain would simply crash into it--which is not necessarily bad for wave propagation type reverse derailments, but could be damaging in the case of backpedal derailments.  And it looks like the K-Edge unit has a fraction of the lateral range of adjustment I gave my unit, but that would only be a problem if you happen to fall outside of their range (for example, if you are running three chainrings).  There are many more machining operations go into the production of the K-Edge units than the Jump Stop, so not surprisingly, there is a substantial price difference.  But for those who don't have to worry about cost, the K-Edge Cross guides offer considerably better protection than the plastic guides, at only 5 to 10 grams heavier--shaving about 10 grams compared to the weight of the Jump Stop.

For single chainring bikes, in cases where it is desirable not to run an outer ring guide, there are also an assortment of seat tube mounted double plate guides.  These resemble a non-moving front derailleur, but operate much closer to the chain, making them more effective as chain guides than derailleurs would be.  Examples in this category include the Roox Chain Dog, the DmR ChainCage, the Rohloff Speedhub System upper chain guide, the MRP 1X Chain Guide for Seat Tube, and Paul's Chain Guide.  Double plate guides have to cope with much greater load stresses than inner guides do, so they tend to be more robustly built, heavier, and more expensive.

Sometimes, it isn't feasible to mount a guide on the seat tube.  For such bikes, another possibility is an E-type mount (named for Shimano's E-type front derailleurs).  These mount under the bottom bracket fixed cup flange, and examples include the JTek DropStop, the MRP XCG and LRP, the K-Edge DIRT-3, the E Thirteen XCX (single ring only) the Blackspire Einfachx (single ring only) and the MSC UltraLight (single ring only),  E-type guides tend to be limited to smaller chainring sizes, and mounting under the fixed cup flange moves the whole crank over a bit, which can alter the chain line, reduce the number of threads available for the BB lockring on the left, and may introduce a clearance problem between the left crankarm and left chainstay, but for some suspension bikes, such a mount may be the only practical option.

Monocoque carbon fiber road bikes present a special challenge because the frame shape and material is incompatible with clamp-type seat tube mounted guides, and the chainrings are usually too large for E-type guides.  For such bikes, K-Edge makes a braze-on mount chain "catcher" (as they call it) which mounts on the derailleur mounting tab (still called a braze-on, even though it is not brazed on non-steel frames).  The arm of this guide experiences considerable cantilever loading, and is probably more vulnerable to damage and going out adjustment because of that, but for many monocoque carbon frames, there simply is no other commercial option available on the market.

This kind of system is for single ring bikes only and operates by having upper and lower idler wheels pressing the chain against the chainring.  Such systems tend to be heavy, expensive, they wear quickly, and they introduce a lot of buzz and drag, but on the single, uncompromising count of keeping the chain from derailing, there is no other type of system which can match them.  Such systems tend to be the best choice for downhill racing, high jumping, and all-around extreme thrashing, but for any riding less extreme, you can still get highly effective protection from many of the systems mentioned above, even for cyclocross and general mountain biking.

In some situations, yes.  It depends on what your needs and priorities are.  If having the the absolute lightest is the highest priority, the Dog Fang or a clone would probably be best.  On a multi-chainring crank, if you have enough room for it, an inner ring guide will usually do the best job of preventing both forward and reverse derailments.  If you are running a single chainring and you don't want, or can't mount, an outer ring guide, almost any double-plate guide would likely be a better solution than my guide, since the Jump Stop provides no protection against outward derailments.  And if mounting on the seat tube is not a viable option, then you are probably better off with an E-type guide, or a derailleur mount guide.  But if you have a standard seat tube with one, two, three, or even four chainrings (including most elliptical rings), and you are looking for good inner derailment protection, the chief strengths of the Jump Stop are reasonable price, reasonable weight, easy installation and adjustment, versatile range of adjustment, easy on the frame finish, good strength, high wear resistance, high corrosion resistance, very effective protection against forward derailments, and reasonably good management and correction of reverse derailments.  If those happen to coincide with your needs and priorities, then the odds are favorable that you will find the Jump Stop quite satisfactory.