This is one of those tools that I never knew I needed until I had it and now I don't know what I ever did without it.I needed itty bitty depressions, and the block has a smallest depression of 4mm in diameter. I was hoping for 3mm, but I suppose 4mm will do.The depressions all seem to be hemispherical (just measured a few to confirm), i.e., each is half of a sphere.1 quality issue:The holes in the wood block to store the punches aren't drilled very precisely. A few of the larger punches don't fit into their respective holes.1 product description issue:The description says: "Punch Head Sizes(mm): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 & 24"This is INACCURATE. Each punch is labelled with a number ranging from 1-24, in order of increasing size, but the numbers do not correspond to the actual size of the punch head. This is just for easy storage -- the holes in the wooden block are numbered correspondingly. The actual punch head size of each punch is also labelled on the wooden block.In case it's helpfulSmallest punch ("punch #1"): 2.3mm diameter spherical headLargest punch ("punch #24"): 25mm diameter spherical head