👉 The mount fluid, also known as silicone mount fluid or EPDM (Ethylene Propylene Diene Monomer) sealant, is a silicone-based lubricant used to ensure a tight, durable seal in O-rings and other seals. It is applied to the mating surfaces of O-rings before assembly to prevent leaks by filling any microscopic gaps or imperfections. This fluid enhances the seal's flexibility and resistance to environmental factors like heat, cold, and chemicals, thereby extending the lifespan of the seal and maintaining the integrity of the system.