Just like the description says...it helps install the headset cups straight into your frame. The are designed for King headsets. I use a Park headset press and these adapters slide right on. If you use the pieces that come stock with a Park HHP2 it will hurt the bearings in your King headset. Save yourself grief and purchase these adaptors if you are dedicated home mechanic. The plus side is all your friends will come over and buy you food and or drinks to let them borrow these when they're building their new bike.