Waterway Plastics 2" Heater Flat O Ring - Pair

Waterway Plastics 2" heater flat o-ring gasket pair

This is the common size used in almost all stainless steel heaters. 

Combination gasket and o ring in one for superior seal - installed each end of the heater tube 
Can be used on many brands with similar mounting - suits:
Gecko, Hydroquip, Balboa, Aquatemp, RMF, etc 

Sold as a pair 
Gasket side - outside diameter - 73mm, inside diameter - 54mm 
O-ring side - diameter of raised ring centre to centre - 63mm