I don't know the open pressure, they are PSI roller springs, the highest RPM was 6500. I followed the link about us cheap Mopar guys after I thought I could use this Chinese stuff. I got lucky and got away with no major damage. The hold downs were Hughes with studs torqued per Hughes recommendation. Nothing I received from PRW was any good, I haven't even got a refund for the damper that didn't fit. Hopefully the flexplate won't shatter on the next run.