Below is a wonderful collection of open-ended toys and Montessori shelf work.
While open-ended toys are great for development, Dr. Montessori also found that children felt a sense of accomplishment from completing a task or 'piece of work'.
Shelf work, like the Fine Motor Set, are defined mostly by their clear beginning, middle, and end. Fitting the egg in the cup builds confidence and satisfaction in work.
You'll also notice that many of the items are made from natural materials like wood, glass, and metal. These are preferred because they provide children with a richer sensorial experience.
Toddlers and young children are sensorial learners, meaning they learn with all their senses. The more we can engage the 5 senses, the more they'll learn from an object.
Think about the feeling of wood or glass - the temperature, the texture, and the variations throughout the object.