Dear Mr. Wenjun

There are several type of belt fabric usually based on material of carcass. For example NN (Nylon,nylon), VN (Vynilon, Nylon), EP (Polyerster) or PN (Polyester,Nylon)etc.
If you are looking 2 PN 500, is mean your belt has 2 ply fabric with 500 KN/cm per ply.
For indentifical the belt specification there are two type to write, eg. :

(a). 1500xEP100x4plyx5mmx1.5mm - Grade M - its mean 1500mm is belt width,EP100 is Tensile strength per ply, 4ply is total fabric inside the belt, 5mm for thickness top cover rubber, 1.5mm for thickness bottom cover and Grade M for grade of cover rubber.

(b). 1500xEP400/4x5mmx1.5mm - Grade M

Total strength of both belt is 400KN/cm.

(a) and (b) look likes similar, but type of (b) stronger then (a) because the Manufacturing can warranty type (b)which has total strength 400KN/cm after processing. In other words, before vulcanizing process the tensile strength per fabric more then 100KN/cm.

Typical (a) has EP100x4ply and after vulcanizing process the tensile strength will be decreased.

Your comments are welcome.