I tend to agree with a review posted by Aiviq, though I'll provide a couple qualifiers. First, I purchased this as the small carry-along device for emergencies, not as a primary fill device (in that form factor you can only pack so much air per stroke so you have to plan to be pumping a while). In my case, it is in my dirt-bike (motorcycle or mountain bike) pack, both of which require lower psi (have not attempted to get my road bikes to 100+ with this device - not saying it can't either). I generally top off my tires with a standard floor pump or compressor at the truck before hitting the trail. I have used this unit for tube replacement (MB), or on trail pressure adjustments (motorcycle). In both cases, due partly to span between uses, I had to sit and scratch my head for a while to remember how to appropriately engage the tool. Once I figure it out again, it does in fact work.So, to date (albeit not too many uses yet), this has served as a functional, very easy to carry trail fix.This bicycle air pump is longer than I expected.The pump is actually 7 inches long and very easy to slide the handle back and forth.It inflates tubes fast for a pump that size.The pressure guage does not work at all.NO DETAILED INSTRUCTIONS on labeled backcard packaging;the first time I attemped to inflate a tire I was unsucessful.I did not TWIST THE ENTIRE DUAL HEAD END OF THE PUMP,TO OPEN THE VALVE,so the air could blow out of it.The instructions say to twist the grey collar to lock.WHAT GREY COLLAR are the instructions on the backcard pertaining to? No lines pointing to the illustration identifying a grey collar that needs to be twisted !This is a very durable pump! It's made right and is small enough to fit in a saddle bag or your rear jersey pocket. I suggest the larger size if you use a pack on your rides to pump your tire up a bit faster. The gauge is quite helpful, especially if you don't have the 'feel' of the tire down yet. It has a dual volume option that is essential for getting the last few pounds of pressure in. Crank Bros have got pumps nailed (as well as pedals)!It really disappointed me to use this pump, had it in my backpack waiting for the right time to use it, and when it came, I was pumping for aprox. 7 minutes until my arms start to feel numb, only to get my MTB tire semi inflated.Great exterior design, but the the pump itself is not what it should.I even watched youtube videos about how to use this pump. It came with no documentation whatsoever on use, and you know I would expect something like this to be self-explanatory, but nothing I did (including the undocumented trick about twisting the grey thing) got it to work. Maybe mine was broken? Maybe it's just a poor design? Maybe I really am stupid? Don't know; threw it out.very good ideas in a product that in the end, doesn`t work.The body is too small to enought air in the tires. The high flow system adds a lot of friction and makes it even harder and the high pressure is the same as a tiny standard pump.Not a single time this was helpful.Crank Brother makes some excellent pedals and multi-tools but this was a bummer.This is a awesome little pump that fit in your jersey pocket perfectly. It has a solid feel when in use so you can get the job done.It can't pump tires on a real bike. It says 115 psi but I can't get 90 out of it. It comes apart easily and feels like a toy. I wish I could send it back but I've waited too long.Sehr zufrieden mit dem Produkt, kann es nur weiter empfehlen an alle die sich dafür interessieren sollten es bestellen sofort.Cet article est arrivé dans les délais. Même s'il est un peu cher, je pense qu'il vaut son prix. Les deux embouts permettent de s'adapter à la plupart des roues.Cette pompe est facilement transportable, pratique d'usage, et permet de gonfler précisément et à haute pression.