This set is for 5-patch blocks of 6 inch square. A very useful set fo making blocks of e.g. Sylvia's Bridal Sampler and Farme's Wife Sampler Quilt. Up till now, there were no templates of the right size for 5-patch blocks (6 inch divided into a grid of 5 x 5).
The book Encyclopedia of Patchwork Blocks volume 4 contains a lot of blocks that you can make with sets L, M and S. Wih set S you make the blocks of 6 inch.