I used them 2 or three times without a problem. I purchased 2 to install a heavy glass shower wall and door. One of them wouldn’t hold the suction. It appeared to have been returned. I asked for a replacement and they both work great.I replace windshields. Yes it works on all glass BUT warps very easy if you do put it back into the box. I went through 2 cups in a year.Good budget toolWorked great!! Lifted very large 3/8” thick glass shower doors. 70” tall 3’ wide. No problem with this.Garbage the suction is not good, if you don't want to lose a foot or a hand I didn't buy itI got this to lay tiles after about 1/2 day of using the suction is not holding at all ... don't waste your money ?????I bought a set of two of these 8" suction cups with plastic handles to move a glass table top. One looks new and holds the suction as expected. The second one was dirty (even the case was dirty) and would not hold suction for even a minute. I returned the defective one and will order another. I can't imagine why they would send out a defective used item. This could have caused damage and/or injury. I'm giving them the benefit of the doubt but if the replacement is defective, I'll change the rating to one star. Update: I returned the defective one and purchased an IMT 8" suction cup with a metal handle. It seems to hold suction; however, the plunger pops out to where the red warning line is showing. The red line is supposed to indicate failing suction. I guess I'm returning these things because I can't trust them to lift my 75 lbs. table top.