They will fit, but will probably raise the front of the XX a good bit(1"-1.5"). 18.125 is .125 longer than the DS450 shocks(18" eye to eye) and slightly shorter than the DS450xmx shocks. Both have been used on the TRX.
i just bought them off a guy. They are Fox Float X Evol Front Shox long travel. they are for houser long travel a arms. I think i got a good deal on them. They cost $1500 new and i got them for $800.00 new on ebay.