Those wheel ramp things for raising a car

I got a pair like that but they are honeycombed underneath and pretty heavy for plastic ramps. I used them mainly for my minivan, no problems yet. I have to brace them with 2X4s up against my garage door so they dont slide when I drive up on them on my concrete driveway. kinda sketchy when one slides and the other holds. And jackstands under the chassis once its up, easy to slide them under and ratchet them up.