O-rings are everywhere until you need one!  Might as well pick these up to have on hand. 

Common sizes for power steering hoses.

• Made of Viton (fluorocarbon elastomer) for use with a variety of chemicals and fuels
• Round cross-section to provide a seal between cylindrical overlapping surfaces
• Can be used across a wide temperature range from -15 degrees F (-26 degrees C) to 400 degrees F (205 degrees C)
• Durometer (hardness) of 75A for resistance to penetration
• Meets standards defined by Aerospace Standard AS568A
• (2) x 5/16" ID - 7/16" OD - 1/16" width
• (2) x 1/4" ID - 3/8" - OD -  1/16" width

CA Residents: Cancer and Reproductive Harm WARNING www.p65warnings.ca.gov.