CAST IRON AIR MIXING CHAMBER W/AIR SHUTTER;1/8" FPT INLET X 1" SLIP FIT OUTLET.;( WAS 7/16" SLIP INLET X 3/4" FPT OUTLET. );IF CUST APPLICATION USES A HOOD ORIFICE (LP) ( # 26-1080 );THEY MAY NEED TO REPLACE ORIFICE WITH THREADED TYPE;ORIFICE (LP) # 26-1225 WHICH WILL ALLOW MIXING;CHAMBER TO SCREW ONTO ORIFICE.