NBR is nitrile butadiene rubber.

NBR foam offers exceptional flexibility and can withstand considerable deformation under sustained compression. It is also highly resistant to tearing.
This material is resistant to lubricants, oils, and certain hydraulic fluids.
NBR foam is used mainly as spacers, dividers, and seals.
It is used in the mechanical engineering, automotive, and the chemical and petrochemical industries.

NBR foam is not resistant to the effects of aromatic hydrocarbons and brake fluids containing glycol. 

It may be combined in copolymers with various other materials.
For instance, a blend of PVC and NBR demonstrates considerable ozone resistance (which cannot be said of pure NBR) and is capable of absorbing impact and shock energy.