Stereognostic bags: This is basically a bag with pairs of wooden shapes. I'm wondering if this tool lacks consistency because different stores have different numbers of pairs of the wooden shapes (some have 8 and others have 10 sets). However, in the Gettman book, 3 different bags are mentioned. Bag 1 is twenty wooden blocks: 10 cubes and 10 rectangular prisms. Bag 2 is 16 buttons with 4 3 cm in diameter, 4 2.5 cm, 4 1.8 cm, and 4 1.5 cm. Each 4 is supposed to be a slightly different shape. Bag 3 has 16 beads with 4 small with large holes, 4 the same size as the first set but with small holes, 4 elongated, and 4 very small. The child puts on a blindfold. For the first bag, they basically use the sense of touch to seperate into piles of cubes or rectangles. The same procedure is used for bags 2and 3 with the child seperating according to touch with their blindfold on. This tool really does seem to lack consistency as several stores have completely different looking wooden blocks. I'd be interested in hearing a Montessori teacher explain this tool a bit more. If the basic idea is to use the sense of touch to match shapes then this definitely looks like a tool that could easily be made, rather than purchasing. For now, I'll be using sets of wooden blocks that we already have. If you want to purchase, it is definitely one of the cheaper tools. For example, at http://www.alisonsmontessori.com/Mystery_Stereognostic_Bag_p/s23.htm it sells for $10.00.