JR Products Black Nitride Shaft Gas Spring. To select a replacement gas spring, remove the spring from its mounting brackets. Measure the Extended Length from center mounting hole to center mounting hole. Measure the amount of piston that is exposed while extended; this is called the Stroke of the gas spring. Select a replacement spring with Extended Length that is the closest to your current unit. Then use either the Stroke measurement, or subtract the Stroke from Extended to find the Compressed sizes that are closest to your current spring. (The measurements do not have to be exact but the closer you can match the original the easier it will be to install.) Selecting the Force: If your current spring has a stamped label the force should be listed within that number. Usually it's the last 2 digits or often followed by the letter N for Newtons (1 pound equals 4.4482 Newtons). This is the pounds of force being exerted to open or hold open the door or platform. It does not equal the weight of the item being lifted. 45570 is 20in Extended Length; 11.42in Compressed Length; 8.58 Stroke; 110 lbs Force. 

MFG# GSNI-7903 GSNI7903 UPC# 756815005289