I have them on a 8 foot door. They stretch out to 71 inches with the door closed seem to work just fine. I do have a safety cable passing through the springs.
As the garage door is the way I come /go in my day, when it broke last week, in the cold, I moderately panicked - - then my hubs found Preferred Doors! Even w/regular shipping it arrived quickly, & the part easily installed (thx hubs)! The email notifications were a godsend, tracking the hours til I could click my opener again! Thx Preferred Doors!
I highly recommend Preferred Doors. I recently purchased a gear and pulley replacement set for my 20 year old Craftsman belt drive 1/2 HP opener. The parts were very reasonably priced and of excellent quality. What set this purchase apart from others was that it included everything needed to do the job, gears, clips, bushings, spacers, grease... They also included very thorough details on how to replace the parts, reset the limit switches test the opener and reset the wireless openers.