Bellaware Colorful Hourglass Sand Timer, 5/10 /15/30 mins Pack of 4

They work fine but ive had them for maybe a week and the black part on one of the hourglasses fell off. Not a huge deal, i will glue again, but i havent had them long at all and pieces are already falling off.

These are freaking amazing!!! They help me keep time with my skills sessions. If you have trouble keeping time, buy these beautiful hour glasses!!!

I bought these for my classroom. It is a very good timer because it doesn't have sound and won't interrupt the rest of the classroom with noise. Students are very receptive to following the rules and are able to tell when their time is up and it's the next persons time. Great for stations and solo time work!

The following recorded study is when the sand stops falling. Not when all of the sand is gone. At the end, all of them leaves a thin layer of sand adhered to the funnel-portion due to high static friction coefficient, or some kind of force that prevents them from falling. All of them fall short, but that is probably by design; typically, you don't want something that deals with time to be longer than it actually is since that will necessarily mean you are too late. I am in accord with the decision made by the R&D to have designed it this way. Furthermore, i am thoroughly impressed by their precision as well as accuracy of these hourglasses that are a few dollars each; good production, sop/gmp.5min: 4:56-4:57 (approx 3 seconds short): -1% discrepancy10min: 9: 51 - 9:49 (approx 10 seconds short) -1.7% discrepancy15min: 14:50 - 14:40 (approx 20-10 seconds short) - 2.2-1.1% discrepancy30min: 29:03 (57 seconds short) - 3.3% discrepancyFor mine, the 15 min timer has had instances where large quantities of it would get stuck on the wall, thus occasionally shaving off upto 10 seconds from the average, but still only adds 1% discrepancy. (here when i say "large" i mean thicker layer/clumps. almost all of them leave a 1-grain thick layer on the glass, which, I would say is negligible (probably would only add about 1-2 seconds even if all of them fell. But occasionally, a larger clump would stay, and this takes away about 5 seconds (but again, 5 seconds is probably negligible to some people).Overall, extremely satisfied for the price, its reliability (precision) and consistency (accuracy).