The replacement Fluval Giant Top Cover Click-Fit O-Rings fit perfectly over the inlet and outlet of the lid on the filter - and they make a great seal so when you click in the AquaStop valves, everything is airtight. The O-rings are suitable for:

• Fluval FX4 External Canister Filter (A214)
• Fluval FX5 External Canister Filter (A218)
• Fluval FX6 External Canister Filter (A219)

Fluval Giant Top Cover Click-Fit O-Rings:

• Easy to replace
• Genuine Fluval Spare Part