What size hat can be made on the different size looms?
The blue (small) loom makes baby hats. You can get good results with one strand of knitting worsted or 2 strands of baby yarn. Another good combination you can try is blending a sports weight (3 ply) with baby yarn. A preemie hat can be made by using 2 strands of knitting worsted weight yarn (4 ply).