Bought material for making 10cm cubes used as math manipulatives for preschoolers . They need to be precise, as they can show no visible deviation when scored every 1 cm, and must stack 9 high in a single stack without falling. 4" is perfect for the raw material, and these are great for a small operation like ours, so we dont have to square/plane/cut the lumber. Perfect! Attached photos are: 1) a hollow sawdust & resin alternative (not great), and examples of math work the 4-5 year old children do with it: 2) stacking materials to understand magnitudes, and 3) doing 4-digit math problems! We ordered one for a prototype, then we order 45-50 for a set. Last week we cut it down to exactly 10 cm with perfect square sides, and tonight we cut the grooves. My son is doing the woodwork for my classroom. He'll do the one set of 50 using your cubes. He'd like to sell more, but unfortunately the CNC router time means only $10/hr for him at this material cost ($350 material + $350 = $700 sale price), so he may need to look elsewhere for the material, or cut his own.