Premium Hutzler 324 Ice Ball Tray - Large 2.5" Ice Sphere Mold for Whiskey, Cocktails & Bourbon - BPA-Free Silicone Ice Cube Maker for Home Bars & Entertaining

They work great with two caveats.First off -- you don't have to fill individual spots from the top,just fill the base tray to the top, not the top of the hemispheric depressions,but to its actual top. Fill preferably with distilled or RO filtered or boiled water for clearer cubes. Then push down the top tray whichhas the holes down on it. Water will squirt out.I then use two rubber bands on either end to hold the tray together,then I place on a very flat area of my freezer, and freeze.If you don't want to do the rubber bands, just put something heavy on top ofthe tray. you will get some frozen water on top, but the little balls pop outeasily. The frozen water on top is kind of interesting ice fora pitcher or something too -- looks like a sheet with holes in it :-)Kids always want more ice to play with and that works fine.You can also try to quickly empty out that extra water, but I foundmyself with many non spherical balls.As you can see, the rubberbands or weights, and flat freezer space arethe requisite caveats.Kotobuki Sphere Ice Ball Tray, Large and the medium size toowork in a similar fashion. I save the big ones for my scotch, and the little onesfor my kids.