30min Sand Clocks Sand Timer Glasshour for Kids Toothbrush Study Cooking 1 min 3 min 5 min 10min 15min 30min 45min 60min Available- Blue 30min

I like the size and the blue color for the sand, but the sand clumps too much making it almost worthless. I've tried to use it about 10 times over the last three days and out of 10+ tries, it has only worked once. The sand stops flowing (most of the time) or a significant portion of the sand hangs up on the walls (twice).I didn't give it once star because it does work if I tap it when the sand stops. I don't need exactly 30 minutes, so this might be acceptable to me. But I am considering getting a different one :/Edit - I just saw in the product description that if the sand gets stuck, to put it in the sun for a while. I tried this and it still clumps up. I even put it in an unheated vacuum oven at work for hours to get rid of any possible moisture. No luck.