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.
Came exactly like the Craftsman repair kit from Sears but only $15 (on sale) other than Sears $40.00 price. Got it in 7 days and working fine. Even came with instructions. Definitely a good buy even at their regular price of $25.00. Save $5.00 sales tax to boot.