edit: 1-30-21 Added 3mm slot box. Looking for a stackable solution for sorting mealworms by size after sifting out frass and bedding. These stack together. There is a solid bottom, 2mm slots, 2.5mm slots and 3mm slot. I plan to use these on a vibration plate to help the mealworms fall through. May have to make the lip that locks them together bigger. Will have to see after first use. Boxes are 147.5mm x 225mm x 40mm. I will be working on larger box sizes so that I can make use of the full print bed.