FABTEK CLR-1 Fin Clamp Hydronic Baseboard Element Additional Fins, 1' Section For 3/4" Copper The 2-1/8" fin will produce 591 btu's per linear foot of active element 2-1/8" fin fits 3/4" copper pipe More durable than original fins, made with heavier gauge metal 1 foot section can be sized to fit your needs, eliminates cold spots