Alvin - Olfa - 300 Snap-Off Utility Knife - The Olfa 300 Snap-Off Utility Knife by Alvin has a fully adjustable snap-off blade secured by a thumbscrew. Loosen the thumbscrew, slide the blade forward and tighten to size. The Olfa 300 Snap-Off Utility Knife includes one Snap-Off blade. Uses OR-AB10B, OR-AB50B, OR-AB10SB, OR-AB50S, and OR-A1160B blades. Alvin is one of the primary sources for drafting supplies and drawing equipment in the country. Creative Coldsnow is a pround retailer of Alvin graphic arts, drafting and fine arts products.