the Cometic MLS HG is made up of three layers of steel, held together by rivets.

On some motors, there can be interference issues with where the rivet tabs are placed.

This one, where the heater return pipe is bolted to the block can be resolved easily: I'll cut the rivet tab off.

This HG was from the first production run. Cometic has since revised the location of the rivet tabs to eliminate such problems.