I’ve used Align 315 and 325 carbons on my B400 and they work well. Just dug around in my pile of nuts and bolts until I found 2 of the same diameter nylon washers that fit. Seems to spin smother. Although I think the B400 woodies have more lift. The 315’s are extremely stable in a low hover. On another note, the trex 450 v1 feathering shaft dampener and the tail shaft bearings are also a cross match. You can’t get (or I haven’t found) those parts specifically for the B400.