With 3 kids in the back seat come this summer, I'm thinking of putting a decent seat cover back there instead of the car-seat pads.

Seems like there are 3 major brands: Wet Okole, Marathon and Coverking. The Coverking site has a lot more material options to help bring costs down.... i'm thinking of the neosurpeme material: https://www.coverking.com/c-6-custom-seat-covers.aspx

Anyone use this brand before?