It's a lil over 1/2inch belt.
I personally love 1/2in belts on hobbits if you know how to tune for them and shim the vari & mod the rear to close completely.
But if you want the best 1/2incher,
Get a dayco top cog, same number I think. The cogs are on top for flexibility and they just last and last and last
Ax/bx40 =42in (edited)