need i say dont use any cinder blocks for any ANY jackstand,, EVER,, i buried one my high school budies,, went back to visit them in tenn after coming home from VN on leave,, had a good day went back next day for lunch with them, kicked his feet stickin out from under 50 ford coupe,, him puttin fresh teansmission in,, went in talked to her , she asked me go get him for lunch before i throw u guys lunch to the dogs, kick his feet again,, didnt move look under there,, cinder blocks under rear axle rubbled,, hes got rear diff in his chest,, was dead when i kicked his feet first time,, dont use cinder blocks for any under car blocking,, use it once youll just keep making excuses to use them for more and more heavier stuff till your blocking your car again an your friends will cfonsole your wife and they will bury you, dont use cinder blocks,, the difference between failing just a little and total failure is zero percent,no significant warning,,, and if you think oh yeah but,, then keep on using cinder blocks anyway,,