Honda Urban Express NU50 and NU50M Belts
Belts used:
Goodyear - Part # 17321 - 17/32" x 32"
Goodyear - Part# 17325 - 17/32" x 32 1/2"
Gates - Part # 9325 - 15/32" x 32 7/8"
Gates - Part # AX31 - 1/2" x 33" (Equivalent to OEM Belt)
Gates - Part # 9335 - 15/32" x 33 7/8"
Gates - Part # BX31 - 21/32" x 34"
Gates - Part # TR22344 - 11/16" x 34 7/8" (Top end belt, Need to use without side cover)
Malossi - Part# 617233 - 19/32 x 34 11/16 or 15 x 8 x 868 32° belt angle
The BX31 is a wider and longer belt which allows higher variation and thus a higher gear ratio and results in much better top speeds.
Malossi 617233 is not as wide or tall as a BX31 and much better quality.
Gathered this information from people on the Moped Army Forum. Please add any information!