L P cookers use three sizes of hob burners. The standard size is the 'semi rapide' burner. Small simmer rings are 'auxilllaire' burners and the large hobs rings are 'rapide' burners.
Over the years L P have used several different types of hob burner. The earilest cookers used the EW burners. These were replaced in 1989 with the MV burners. The MV burners were replaced with the ECO burners in 2003.
The most recent change is to the SC burners for the 2011 season.
Unfortunately these different burner parts are not interchangable between the different types.