The HSP-P5 is simply a square piece of steel that slides over the Oz-Hammer (OH-01) and keeps it centered on the inside of the Oz-Post sleeve when installing the P5-850. This Hammer Spacer is used in conjunction with the OH-01 Oz-Hammer. The OH-01 Oz-Hammer is 2” in diameter. The P5-850 is 5” inside diameter so we recommend using the HSP-P5 to keep the Oz-Hammer (OH-01) centered in the Oz-Post sleeve during installation.