i was unaware that cinder blocks were different from cement blocks. i will google them to find out, but i was using the term cinder to mean cement. the more i thought about it i finally realized that all the years i worked at marinas we used cement blocks to support 25 ton boats with no problems. the only time the blocks cracked was when you tossed them and they bounced off each other and cracked in half. the way bob is using his to hold up his vert is incorrect as the holes should face up for maximum strength. however, in his defense he has the block, the bumper jack and the floor jack at work so his car is safe. i always use some wood blocking on top of the block so the car never rests directly on the block. anyway, if they are good enough for 25 ton boats they should be good for a 2 ton car. dennis