The Crack-Pac is a two-part, low viscosity crack injection epoxy designed to repair cracks in concrete.The mixed adhesive has the viscosity of a light oil and a low surface tension which allows it to penetrate fine to medium width cracks. Resin is contained in the cartridge and hardener is contained in the nozzle. Once the nozzle is threaded onto the cartridge, the hardener is released into the resin-filled cartridge by turning the knob at the base of the nozzle. The two components are mixed by shaking the cartridge.