in {TAIL ~ step} the first cooktop unit is preassembled with one cooking system type and {HEAD ~ the second cooktop unit} is preassembled with a different cooking system type prior to mounting on the base units 
in { TAIL ~ step } the first cooktop unit is preassembled with one cooking system type and { HEAD ~ the second cooktop unit } is preassembled with a different cooking system type prior to mounting on the base units
REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH