What a great add to my bike. I looked at several of these and chose this one since it doesn't rely on tiny set screws to stay on. The inside of the bezel is threaded so it stays in place.The instructions are impossible to read, but it was straight forward enough to go on quickly and securely.The entire bezel unscrews from the base. Once off, you can pop the clock out to set the time. It has a stem that you pull out with a finger nail, turn to set the time, and click back in. Make sure the O ring is in place before clicking the clock back into the bezel.Before installing it on the bike, screw the bezel to the base tightly and mark the front of the base (12 O'clock) with a dot (sharpie). Unscrew the bezel from the base.Remove your existing top cap and use the bolt to attach the base, taking care to put your mark forward on the bike. Screw the bezel to the base and turn it until its straight.You are done.I bought another for my other bike.This is a nice feature to add an analog clock to your bike. On top of the stem is a perfect spot. One caveat though; the glass covering the face is thin and fragile, I broke it when I placed my backpack on top of it. This is my second clock because I like it so much!i got the idea to do this after seeing berm peak on this. i saw several here that looked basically identical to that one. i finally decided on this based on the cost and materials used.after thoroughly going over all the product details i chose this. granted with current global cargo issues ongoing i was concerned there could be transit issues, but thankfully there were none whatsoever.the clock is just as described here. it is constructed using a metal frame, glass crystal and solid/good plastic body. a battery is pre-installed, just push the clock stem back in and it starts running. *FYI to save battery life you can do the opposite. simply pull the stem out and you stop the clock and any battery drain.the clock is basically three parts. the threading is good so no problem taking it apart and reassembling. that said be careful not to misplace the silicone O ring that protects the internal parts from water intrusion.to install it couldn't be easier. there is just a single bolt holding the stock cap in place on the bike. unscrew it and place the lower colored metal section in place. then tighten down and screw the upper portion. this part took me the longest to get right. if you don't have the threads lined up right, bottom and top, the clock won't be centered once fully on. to get this right i needed to unscrew the lower portion and turn it a bit so the threads were moved some. then i slightly turned the top so the threads would grab in different spots. on the third try, turn i was able to get the "12" lined up vertically.the entire process start to finish took me all of maybe five minutes? the clock is nicely made, better than i expected. it keeps time the same as any other battery clock combo no noticeable gaining or losing minutes.if needed i would purchase this again. a good add-on for a bike to give it a little unique character.Like the idea and the looks. Nice to have something analog on the bike. But a watch should, you know, keep time. This one went nuts after a couple of months. Two hours slow, then too fast. Like I said, it looks nice.I was reading it was for cruiser and mountain bikes and didn't really look at the measurement of the hole that was needed for this to fit. I have no idea what bike this will fit, but it wasn't any of mine. This was eturned.Perfect for me to tell how long I am riding.Producto que no funciona , creo ,con la bateria agotada , ya es el segundo que compro y los dos igual .Aconsejo que Amazon no comercialce este producto ( no lo compraré mas)