The Clan LB2-X is 30 hexes, and based on JJ distances(multiples of 30m x hexes travelled) and
the MKII's fluff(450m being the range where the 15 hex Clan ER Mediums come into play), hexes are 30m across, therefore 30x30=900m.
While we're at it, if all retail MC2 mechs were jumping 125m(just over 4 hexes), then ranges were definitely out of whack(though to be fair, weapon ranges would be
stupidly long from a view perspective if we were to use that for a basis; Clan ERLLs would have a max range just over 6x the standard 4-hex jumping distance, or a bit over two fully zoomed out(MC2 retail) screenwidths @ 1280x1024), and the Heavy AC(20) on a Hunchback would still be able to reach across the better part of one same screen(9 hexes, or over twice its jumping distance).