I had help ordering the 5/8" seat spacers in order to get my subwoofer box installed correctly. The instructions were spot on! It was harder to take the rear bolts out than it was to install the spacers - lol.
Really wanted to be able to fold down the rear seat after installing this but it looks like you’ll need to raise the seat at least 1 1/4” in order to accomplish that.
As far as increasing box volume for subs this doesn’t do a whole lot but I did not buy for that reason.
I’m going to use these as a template to make 4 more and find some longer bolts my self. Hence the 4 star review.