Abstract: A power transmission belt with a good balance of high temperature resistance, good belt durability and low temperature flexibility, and a service range of about −40° C. to about 140° C. The main belt body portion of the power transmission belt is manufactured from an elastomeric material comprising 100 parts by weight of an at least partially hydrogenated nitrile group-containing copolymer rubber, and from about 0.5 to about 50 parts per hundred weight of said rubber of a fiber reinforcement having a length to diameter ratio of greater than 10:1.

Abstract: A flexible shaft coupling element comprising a sleeve shaped body having a central annular portion and a coupling receiving portion at each of two opposing sleeve ends. The coupling receiving portions include axially extending teeth on their inner surfaces. The flexible shaft coupling element is characterized in that the annular portion possesses a torsional shear capacity and the area defining the axially extending teeth possesses a shear capacity, and the tooth shear capacity exceeds the annular portion torsional shear capacity.