Like the dual dawgs on the 441, least keeps the muffler and saw from beating on the wood when sawing.
I've just bought a MS311(is not as good a saw as my old magnum but a really good end of financial year sale and a 40% instant tax write off for me) as a lighter firewood saw to back up my 038Magnum, I've had to put out two small fires in the first three hours of use due to the muffler sitting in bark as the standard dogs are shite and too small.
Looking for a bigger dog asap, the chain cover is cheap plastic without holes so can't fit an extra dog but one good inner one should be sufficient.
edit: do most stihl dogs fit all stihl saws?