DOP11023STMS250 Stihl MS250 42.5mm Cylinder Assembly No. 1123-020-1209. Up size your 025 by .5mm. Up size your 023 by 2.5mm. This is a ecomony aftermarket replacement cylinder. Replaces Stihl part numbers 1123-020-1209, 11230201209, 1123 020 1209, 1123-020-1227, 11230201227 and 1123 020 1227.