Hardener 205 is perfect if you need a very fast curing resin. WEST SYSTEM 205 fast hardener is the best choice in cold weather. Mixed with the 105 resin in the ratio of 5 parts resin to 1 part hardener, the cured mixture yields high strength, durable and cohesive properties. It has excellent moisture vapor resistance. Setting time: 10 - 15 minutes at 21°C. At 21°C, it cures into a solid mass in five to seven hours. Fully cured after several days.