There are 4 different bar lengths in Rollomatic ES available with the 3003 mount which suits the 064-MS660 series.
Regards
Phil
Me thinks you boo booed? Sure you didn't mean MS880? MS660 and MS880 have different mounts.
MS660 takes the standard Stihl 12mm slot bar, the MS880 takes the 14mm bar
But anyway, .404" in my book and experience has a number of advantages over 3/8". Loggers that fell Stringybark for example favour .404" due to the wider kerf and less bark getting jammed. On long bars .404" clears chips better. The second I converted a 42" Oregon Power Match Plus from .404" to 3/8" it started having all sorts of chip clearance and jamming problems in certain types of wood. This isn't noticed when milling however due to the direction of the grain cut (smaller chips) and this same 42" bar works a treat when milling with 3/8", cross cutting in some wood it's a pig with some nasty kickback tendencies from the 3120 when the chips jam it up in the cut.
Even on shorter bars I believe it has the wood on 3/8",
providing your saw has the nuts to pull it swiftly and it has been set up correctly. When you take into account how much longer the chain stays sharp,
plus how much longer the cutters can be used before the chain gets thrown away and it becomes far more appealing.
I ran a 20" .404" .063" Tsumura with semi chisel on my modded 7900's for a while and I was a big fan. Unfortunately I had to come to terms with the vast array of chains hanging in my shed and my failing memory as to just which saw and bar they belonged to
I swapped the tip to 3/8" once that one loop of .404" wore out as I already had a swag of 72DL 3/8" .063" chains there to use. No regrets and the guys flaming anybody that uses .404" should remember that cutting cants and racing is far different to felling or firewood cutting in the field.