If you want to have a complete tool box, you need the Allen key set (8 pieces). It looks like just like a Swiss knife but instead it contains Allen keys. This Allen key set is lightweight, versatile and takes up very litte space (Approx. 10.8 x 2.3 x 3.3 cm). In addition, the keys are fixed to the stand so you won't lose them. Each Allen key has a different size (6 mm, 5 mm, 4 mm, 3.5 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm).