Diaphragm for OMC Double Line Pressurized Tanks 
OMC  30256, 305715  

This is for the old OMC Pressurized Double Line gas tanks. 
There are two different styles of the diaphragm.  One has an extra small hole in the upper center - the other is solid.  (See Pictures) 

The oldest of the tanks has a metal button and fuel pump push rod fits through that small hole.   
The later version uses a taller black plastic push button only and uses the solid diaphragm.  

Please select the style when adding to your cart.