Based on a review of the #506 (3/8 inch) braces by one person who found that the design had changed I thought , a small clarification of the top design. 1/4" #504, 5/16" #505, and 3/8" #506 staples have diagonally (45 degrees) cut tips for penetrating hard surfaces (such as roofing felt if they are be stapled to plywood.) other tip design that is flat and chiseled. It is designed for softer surfaces (substrates) that require a longer hold. with a gun.