The 250 is the largest displacement of that series of Stihl Chainsaws.
At the purchase of the later Stihl 025 I have, I thought it was cute, and clean, and showed interest but after examining it, I saw that it was a clamshell saw.After pulling on the cord, I bought it.
Not having much hope for high Stihl performance from it, at home I started it up and made a couple cuts and was pleasantly delighted that it had a proper mixture in spite of the muffler mod and single needle carb and how well it cut. It had a yellow chain.
I read a little about them and reviewed IPL's and pulled the muffler on mine and saw that it was a four port one like a 250.
My 025 is a .325 X 16" one.
Some are 3/8LP.
Some are 18".
The bar is a different mount than the 026/260 and most have spur sprockets.
Except for putting a new twin needle carb on it, I have changed nothing on it since purchasing it from a fellow Chainsaw Repair member.
He ran it back in the winter in a comparison with a 40cc chainsaw and there was no comparison, the Stihl 025 run off and left the 40cc chainsaw in the dust.