Hi-Q Coupling Half, 0.50 Inch Bore, -- Inch Key

Urethane spiders handle a much wider cold-end range than Buna-N. You're looking at minus 80 degrees F on the low end, up to 180 degrees F on the high end. Buna-N only goes down to minus 20 degrees F, so if your setup runs in a cold environment or sees any real temperature swings, the urethane gives you a lot more headroom on that lower end. Both top out the same at 180 degrees F.

With a 0.50 inch bore, it is sized for a 1/2 inch shaft. This is a Hi-Q coupling half commonly used to couple a hydraulic pump to an electric motor, and it is built to help avoid metal to metal contact while handling small alignment errors.

This coupling half can handle a maximum angular offset of 1 degree and a maximum parallel offset of 0.015 inches, making it suitable for setups that aren't perfectly aligned.