Rebound 25 is an easy-to-use platinum-cure silicone rubber which self-thickens for making brush-on molds of almost any model. Mixed 1A:1B by volume (no scale necessary), you can apply Rebound 25 rubber with a brush or spatula to vertical surfaces without sagging and will cure with negligible shrinkage to a flexible rubber.
Rebound 25 is soft, flexible and is good for making molds of models with deep undercuts. Depending on model configuration, Rebound 25 can be inverted as a glove molds. Rebound 40 is harder and less flexible. These products are compatible. For example, you can apply two coats of Rebound 25 and back it up with two coats of Rebound 40.