The Swiss Tech 10PK 18mm SK5 steel replacement blades, fit most 18mm snap-off knives Storage case included,heavy duty, silver, snap off, blade, high quality, long lasting, SK5 steel for durable professional performance, always sharp, simply snap for new sharp edge. Our blades are designed to minimize risk of cutting injury and protect contents in cartons and packaged goods. heavy duty SK5 steel utility blades stays sharper, longer life than standard carbon blades. Swiss Tech 18mm Blades - 10 Pack are engineered to fit Swiss Tech and most standard utility knives. Shatterproof bimetal construction of the blades allows the blade to bend and bend without breaking. Talented design allows the blade to extend further to achieve deeper cuts and the application of cutting dry wall, insulation etc.