Rebound™ 40 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), Rebound® rubber can be applied with a brush or spatula to vertical surfaces without sagging and will cure with negligible shrinkage to a flexible rubber.
Rebound™ 40 is hard and not very flexible. It is compatible with Rebound™ 25. For example, you can apply two coats of Rebound™ 25 and back it up with two coats of Rebound™ 40.