18" .325" Pitch .063"Gauge 68 Drive Link Stihl Rapid Duro 3 Carbide Chain fits Ms230, Ms250 and Ms251 Saws Applications: The RD3 chain is especially suited for cutting dirty wood, treated wood, roots and hardwoods. The first STIHL carbide-tipped .325" saw chain stays sharp up to four times longer than standard chains. In addition, the STIHL RAPID Duro 3 is a low-vibration chain with a reduced kickback tendency. Please note this chain will Only Fit the Stihl MS250 and MS251 chainsaws with a 18" Bar 18" Bar Size, 68 Drive Links, .325Pitch and .063 Guage Will fit on MS250 and MS251 Saws