These 40lb air springs work great with the top glass door of my camper trunk, Leer. The previous owner had retrofittable 40lb and 30lb models installed which worked fine for a few years but then they failed to hold the glass in the cold weather last year. After the glasses fell on my head, I figured it was time to change them. These 2.40 pound attachments snap directly onto the balls on the RV's body and door, perfectly holding the door. I'm not used to air springs working so well that I had to replace others a year ago. The first time I opened a jar, it almost hit me on the chin. But I'm looking at it now with the glass coming up.