Just replaced mine (4 yrs. old/one side had lost pressure) with a pair from NAPA. If you look at the strut, the manufacturer and part number are stamped on. Internet search gave me the extended/compressed lengths as well as the force. Wasn't able to purchase direcetly from Van's supplier (off-shore mfg.), hence NAPA. If you go the same route, be careful that the numbers match up, or you could damage your A/C. My NAPA set has 1 in. less extension, so top of canopy is probably open 2-3 inches less. Buy a set from Van's if you have the time. Price about the same as NAPA. Suggest replacing both sides.
Terry