Groove Size: .375" dia. x .125" wide Material: Black SBR Rubber, 60 Duro Used to seal the 1/4" copper tubing to the water reservoir from the steam trap or bellows Included in: Steam Trap (New Style/Upgrade Kit) (RPI Part #MIK078) Fits: Water Reservoir to 1/4" Copper Tubing, Groove Size: .375" dia. x .125" wide (Older Style Units Only)