The HSP-C175 is simply a square piece of steel that slides over the Oz-Hammer (OH-02) and keeps it centered on the inside of the Oz-Post sleeve when installing the C175-850. This Hammer Spacer is used in conjunction with the OH-02 Oz-Hammer. The OH-02 Oz-Hammer is 1 1/8” in diameter, so when installing the C175-850 which is 1 3/4” we recommend using the HSP-C175 to keep the Oz-Hammer (OH-02) centered in the Oz-Post sleeve.