The measuring chamber index pin must fit in the notch in the upper housing. If the pin or slot is badly worn, extra care must be taken to be sure the measuring chamber is properly oriented.Measuring Chamber / Disc Data
#5 Half Ball 1.245 Inches (Undersize)Parts Interchangeability (5/8 Inch Arctic)
#6 Half Ball 1.246 Inches (Standard)
#7 Half Ball 1.247 Inches
#8 Half Ball 1.248 Inches
#9 Half Ball 1.249 Inches
#10 Half Ball 1.250 Inches
#11 Half Ball 1.251 Inches
#12 Half Ball 1.252 Inches
Chambers from Arctic (not Tropic) meters generally work in 504 meters, but they corrode quicker.
Arctic and Tropic meter internal gear trains generally work in 504 meters.