P/N is 57001-1511 for P650 and 57001-1519 for P360. MSRP=$14.88/ea (dealer might charge you higher). This tool tells you whether the belt is IN spec or OUT of spec. It does NOT tell you the absolute width in units. It's a simple/cheap looking plastic template (should cost only about $0.49, but it might be worth having one because the correct technique to measure the width is too awkward and cumbersome.

 

I just use my dial calipers and steel millimeter ruler.