O-Ring Part Number: A20038 / A-20038 (2-Pack) Compatible with Fluval 104, 105, 106, 107, 204, 205, 206, 207, A201, A206, A202, A207, A440, and A443 canister filters. Designed to seal the motor head/lid to the filter canister for the models listed above. This pack includes two (2) O-rings (also referred to as seals or gaskets). Replace your leaking O-ring and keep a spare for future use with this convenient 2-pack.