Plug Followers

If you want to take a lock apart plug followers are a handy tool to have. A plug follower is placed into the lock housing while you remove the core.
You can try removing the core without a plug follower but be prepared to see springs and pins flying everywhere.
This set of four anodised aluminum followers are designed to fit the vast majority of different sizes that you will run into.

For the for professional these tools are essential - for the hobbyist they are really nice to have

Sizes 0.5, 0.55, 0.498, 0.398

If you get a set of plug followers you should also pick up a pair of pinning tweezers