The extra holes in the front of the case look to me like the holes for the metal shield used on rescue saws to protect the front of the case. Back to the bar. How do I find what roller tips can interchange to change to a 3/8ths? Been down that road and the dealers seem to have no knowledge.Tell me 404 is all that is shown in the catalog. Actually, the page did not show any of the saws ending in 4. 066, 088, MS880. 066 of course is the small mount. I have no pattern or schematics to hack the small mount to fit and what really ticks me off is I could buy brand new small mounts bars much less than I paid for these used bars that were to be large mount but not. I have a lot of NEW unused 3/8" 135 driver ripper chains, just need a bar.