http://www.polymersealing.com/pdf/cat_oring_001.pdf -- the best information I've seen on the net. Also, a free downloadable program called "inphorm" for O-ring design is at-- http://www.parker.com/inphorminfo/ Select "Use It" and download the o-ring program which allows you to select o-rings based on various design criteria. William Alford walford@dbtech.net Tout comprendre c'est tout pardonner