D&D Global 335J21 Micro-V Serpentine Belt - J Section, 21 Ribs, 33.5in 1.7/8" What does the 5M in

What does the 5M in 1110-5M-25 mean

"name":"D&D Global 295K13 Micro-V Serpentine Belt — K Section

"mpn":"TB072053916904"

Need a quote on 1248-8M-85

"name":"D&D Global 150T5/180US Timing Belt — T5 Section

D&D Global 335J21 Micro-V Serpentine Belt - J Section, 21 Ribs, 33.5in 1.7/8" What does the 5M inThe D&D Global 335J21 is a Micro V (multi ribbed) belt with Micro V ribbed J section dimensions, manufactured by D&D Global. Micro V belts deliver smooth, quiet operation with high power capacity in a compact cross section, ideal for serpentine and multi accessory drive systems. Constructed with Neoprene body compound and polyester cord tensile members for reliable power transmission and long service life. Specifications Belt Section J Belt Type Micro