i am pretty sure the un-72 is being phased out as well, it's successor being the un-54? or at least you can use a un-73... either way they are both hollow spindle and come in sizes from 103 all the way through 113+. remove it from the frame before you try and measure it, it will save you headaches of eyeballing a tape measure and being off by 1 or 2mm. when in doubt, hit up your LBS with old bb in hand and leave it up to the guys who play with that stuff for a living. they are cheap as fock and available at any shop thats worth its existence. hell even nashbar sells them for under 25 bucks. oh and unless you have the LBS install it, you'll need a park tool bbt-2 (i think is also discontinued, may be the same as the bbt-22 now...) bottom bracket tool which hooks onto a standard 3/8" ratchet or can be cranked by a (i think) 32mm hand wrench to screw in the "cups." good luck.