Darcoid NBR (Nitrile Butadiene) Material Compound Data Sheet #1288. Original test data stored in the Darcoid Compound Database. This material is available to run in our manufacturing partner plant in N America and Hardness Shore A (+/- 5) is 70. NBR (Nitrile Butadiene) meets MIL-STD-417 Type S Class SB 720 A1 B1 E1 E3 F2 certification.