This Genie chain drive bullet assembly is the white piece that holds the chain for the garage door opener together. Works with chain model Genie garage door openers that have a C-Channel rail. The chain carriage assembly for these models also attaches to this chain bullet assembly allowing it to move the garage door open and closed up and down the rail. 

• Assembly contains: The 2 Bullet side white pieces, and the four screws to install it
• Genuine Genie replacement part 
• Compatible with Genie models that have a chain rail: 1028, 2028, 3020H, 3020H-B, 3024, 4024, 3022, 3042, 3120H, 3120H-B, 4022, 4042, 4124, 4164 (ChainMax, ReliaG, IntellG, and TriloG, series with these model numbers)