Celestron 8 inch (20 cm) f/10 SCT with orange optical tube and factory set-style collimation screws.
Note1: These knobs will fit C8 models made prior to 1980. These can be identified by an orange optical tube and factory set-style collimation screws with a fourth central screw in the secondary housing.
Note2: Two sets of knobs are included with your order. One set has 3/8" long screws, and the other set has 1/2" long screws. Use the screw length that fits your telescope best. There should be two or three screw thread turns above the secondary housing and the dust cover should fit without contacting the knobs.