All the Pro Series Mechanicals are compound approved for any set-up. They feature the New PRO TIP and “Snap Cup” design which holds all components in place for easy installation on your arrows. Super strong, razor sharp .035 stainless blades. No O rings , bands, or clips. Blades stay closed out of the fastest bows yet open smoothly on impact! PRO 3-BLADE (1-3/8") - 1 3/8” Cut diameter. Our original all around workhorse, 40-degree swept blades for better penetration and our new PRO SERIES TIP!