Methyltrimethoxysilane (MTMS) is an organofunctional silane. It is used as a coupling agent in thermoplastics and thermosetting resins, as a cross-linker in silicone sealants, as a water-repellent component in hydrophobic surface treatments and sol-gel coatings, as a monomer, catalyst, surface modifier and intermediate, and in household products for conditioning and waterproofing leather. It is a clear, colourless liquid. Recorded grades include technical, high-purity.