This Chain Drive Sprocket sits on the shaft on top of the power head. The chain goes around the sprocket and the teeth on it grip the chain so it stays on track. This is used on multiple Genie model garage door openers that have the chain drive rail system. (See below)

• Compatible with Models; 1028, 2028, 1128, 2128, 3020H, 3020HB, 3024, 4024, 3022, 4022, ChainMax 1000, ReliaG 650, ReliaG 850
• Genuine Genie Replacement Part