Spring loaded adjustment, works like a pocket knife and allows the correct size to be used every time. Small enough to fit into your pocket, and packed in a sturdy material pounch. Special spacer blades lift into place for a snug fit that eliminates the play of most adjustable wrenches. 12 SAE sizes range from 5/16" to 1". Folds down to an incredible 5 x 2 x 3/4". Ideal for: cars, boats, caravans, motorcycles, trucks and kitchen drawers.