A-2 is the key low component — and everyone knows it. On low boards, assume other A-2s exist multiway. Nut low chopped → you only get a quarter if someone scoops high against you.
Preflop implication: A2xx is playable a lot — but A2 with no high potential and no backup low cards can still be awkward. Prefer A2 with another low and/or suits that can scoop.