This barrel nut screwdriver is designed to accommodate nut sizes 6 through 10 and has a wider blade. The shaft length is approximately 8", making the overall length approximately 13". The blade is 3/8" wide to better accommodate the barrel nut used with the Type 13TB4 terminal board used in the Symbol 400.1 and Symbol 400.2 terminal boxes. The thickness of the blade may not allow it to fully seat in the barrel nuts for the 13TB4 because the slot-width is too narrow due to what we believe is an error with the controlling specifications. You may have to grind the blades to fit them. The Comsaco part number is 404261-005.