After I went way to hard on my bike in the woods with my friend (being the test-monkey in up to 20" deep puddles), my rear derailleur broke, so my mom, the real user, bought me a new one. It shipped here in about 4 days. When I got home from school and found it sitting in the box, I was EXTREMELY excited. I went into the garage, placed the tools on the ground, and started fixing my Schwinn bike. I thought it was going to be hard, but it was a piece of cake. I didn't even need the instructions! Who says fixing these parts of a bike is impossible? It's indeed a good product and is easily put on. Luckily, it didn't need any assembly and came in 1 piece. Now, my rear derailleur might break again cause I ride the bike way to much!!!!! I ride the bike every day about a mile and listen to my Ipod the whole way. I'm so thankful my bike is fixed. This is a good product and if you have doubts about buying this, back-up and rethink your answer. GOOD PRODUCT!!!!!