3V & 3VX belts topwidth is .38" / thickness is .32"
A, AX & 4L belts top width is .50" / thickness is .34"
B, BX & 5L belts top width is .62"/ thickness is .44"

C & CX belts top width is .87" / thickness is .55"

D belts top width is 1.26" / thickness is .86"

5V & 5VX belt top width is .62" / thickness is .55

8V belt top width is 1.00" / thickness is .93"
See belt cross reference for 4L to A and 5L to B sizes

A & AX Size v-belts Nominal length = Inside length / Outside Circumference = Inside length + 2"

B & BX Size v-belts up to 210 Nominal length = Inside length / Outside Circumference = Inside length + 3"

B & BX Size v-belts 214 & up Nominal length = Inside length / Outside Circumference = Inside length + 1.2"

C & CX Size v-belts up to 210 Nominal length = Inside length / Outside Circumference = Inside length + 4"

C & CX Size v-belts 212 & up Nominal length = Inside length + 2" / Outside Circumference = Nominal length + 2" 

D Size v-belts up to 210 Nominal length = Inside length / Outside Circumference = Inside length + 5"

D Size v-belts 225 & up Nominal Length = Inside length + 2.5" / Outside Circumfernce = Nominal length + 2.5"

3L, 3V, 4L, 5L, 5V, 5VX & 8V Size v-belts Nominal length = Outside Circumference in inches and tenths