MRP’s new 2x guide is designed to do four things, and four things only: prevent the chain from derailing from the underside of the chainrings; prevent the chain from falling inboard from the small ring; quiet down the drivetrain on rough trails; and provide chainring protection with its bash guard. It does these four things well, but its lack of big-ring chain guiding ability up near the front derailleur means it doesn't provide complete security.
The bottom bracket mounted version of the 2x is quick and easy to install, and doesn’t require breaking the chain to do so. The instructions are simple yet informative and easy to follow, but were only used as a double-check after we blindly (and successfully) installed it. Rear shifting didn’t seem affected by the device at all, and only a microscopic delay in front shifting speed was occasionally discernible.
Neither of the MRP’s two pulleys made more than a whisper of noise while shifting or pedaling, and they could only be heard on smooth hardpack when breathing wasn’t hard. As soon as knobby tires hit loose trail, or breathing turned into a rhythmic pant, the pulleys' sound was drowned out. Additionally, the system did its job quite well at combating chain slap, so the slight hum on the smooth stuff seemed more than worth the silence and lack of frame abuse when riding real trails.
Throughout our test period using the 2x on a 5in-travel bike on a good variety of terrain, it lived up to MRP's claims. Efforts to back-pedal the chain off both the big and small ring were consistently thwarted, and the chain never came off from the lower edge of the chainrings. The inner plate that’s designed to keep the chain from falling to the inside of the small ring worked very well too, even with an intentionally mistuned front derailleur. We gave the removable bash guard a handful of gratuitous bashings and it held up without flaw.
For riders looking to remedy any or all of the four issues mentioned in the intro, the 2x is a great option. However, we found we still regularly lost the chain from up top. MRP don’t claim any improvement in chain retention in this area compared to a front derailleur but it's annoying to lose a chain while running any type of chain guide. Maybe MRP will eventually offer an outer guide similar to their Carbon Guard Ring that's compatible with 2x10 cranks but until then, don’t expect the 2x to be an end-all solution to chain loss issues.