This 20" guide bar is compatible with STIHL chainsaws and is designed to fit D025 mounting. It is a high-quality Oregon chainsaw guide bar made from durable materials to ensure a long-lasting performance. The bar uses 3/8 pitch .050 gauge 72 drive links chain size, making it an ideal replacement for the original Stihl 3003-812-8921. This guide bar is perfect for those who need to replace their old or damaged one and want to have a reliable and efficient tool for their chainsaw. I Whether you are a professional or just a weekend warrior