mostly plastic, which could be an issue. large size is still a snug fit with a size 14 boot.
hi-back is, very high, even at the most upright stance you have a relatively forward, forward-lean, it took some getting used to but i now enjoy it, i believe burton makes a lower back which you could swap out if you needed to
ratchets are high quality, don't get jammed up with snow. the toe cap stays on well with burton boots, but my friend borrowed the board and had trouble with his non-burton boots.