which one of these urethanes
75-80 RTV Liquid Urethane Mold Rubber
Mixed 2 Parts A to 1 Part B
Working Time: 45 Minutes
Hardness, Shore A: 80
75-60 RTV Liquid Urethane
Mold Rubber
Mixed 1 Part A to 1 Part B
Working Time: 15 Minutes
Hardness, Shore A: 60
74-30 RTV Liquid Urethane
Mold Rubber
Mixed 1 Part A to 1 Part B
Working Time: 30 Minutes
Hardeness, Shore A: 30