The Mystery Bag with Matching Items (D108-3) is a classic stereognostic sense material in which the child reaches into an opaque bag to identify objects by touch alone, then matches them to identical control objects placed outside the bag. It directly exercises the stereognostic sense as defined in Montessori sensorial theory and builds the child's capacity for conscious muscular memory, making it appropriate for primary children from approximately age three onward. This version's matching format allows for clear self-correction and makes it especially suitable for independent work by children who are still developing their sensorial vocabulary.