OLFA® STAINLESS STEEL™ blades are sharper than most other snap-off blades in the world, and rust-proof. This makes them perfectly suitable when things can get a little wet or moist. The stainless steel blades will also not scratch glass, making them perfect for the window tinting industry. During the manufacturing process, the following factors are perfected to ensure a good balance between sharpness and long life: Hardness Sharpening Angles Tapered Dimensions Coarseness of whetstone Speed of grinding This 9mm size is 0.38mm thick and has 13 snap segments. The plastic pack has a useful section which you can use to snap off and safely store used blade segments.