All our post office auger round urethane belts come with our Super-Strong Welds warranted not to break at the weld. Standard cross-section diameter is 4 mm, but other sizes are available. Red 90A durometer. Stretch 8% Green -- Matte surface 88A durometer. Stretch 9% Rough surface 86A durometer. Stretch 10% Clear 83A durometer. Stretch 12% HT (High Tension) Blue 85A. Stretch 20% Time tested and proven long life on Siemens facer, canceller,and sorting machines. NSN numbers available on request. For the best in postal round polyurethane belts and post office auger belts, insist on DuraBelt.