My toddler likes colors in the bath water. The commercial bath bombs, even the crayola ones for kids were getting a bit pricey so I wanted to make my own. All the molds I saw on here were too large for his mini tub, so I made a customizable one. id is the inner diameter of the tube, and sphereR is the radius of the top and bottom spherical surface. height is the height of the tube, with a bit of trial and error you can size it right so filling it will be the right amount for one. If the mixture starts sticking I spray a little cooking spray on the top and bottom surfaces. To use this simply print all three parts, put the bottom in the tube and set on the counter, fill with mixture, and push the plunger in as hard as you can. Then take the bottom back off, and use the plunger to pop out your bath bomb and let it dry.