I was going to get the "severe duty" 7,000lb single convolution Timbren for my 1500 Sierra as recommended by Timbren for slide in camper applications, but couldn't find stock of them so went with the 6,000lb double convolution instead. They work incredibly well and are dead simple to install. I doubt I would have noticed a difference between the two, but I'm not too overloaded I don't think either. They definitely get squished when I'm loaded though. Smooths out the ride a lot. Good luck!