The above mentioned hammer part number is wrong. If you have a 2005 or newer USP compact, and want a spur hammer you will need part #214825 this is the NEW hammer. It has the slot cut in it for the newer style catch. I found out the hard way and now have to exchange it. I am only posting this because I used this thread to confirm (wrongly) that I had the right part # (and it wasn't). No biggie, but just in case someone reads this later on.
Just to be clear on the part numbers:
If your pistol has an all metal hammer on it- you need 214301 this is older
If your pistol has a rubber tipped hammer- you need 214825 this is newer
Another way to check is to look in the back of the slide with the hammer cocked. You will see on the right side the catch. It sticks out about .2-.3" and goes into a cut in the hammer on newer pistols, slowly let the hammer forward and you will see the catch go into this slot (look kinda down on to the pivot point of the hammer). If you see this your USP is a newer pistol and needs #214825.
ETA: No ones fault in here, just trying to be helpful in case someone looks this up.