i recently built up a singlespeed with a freehub and a spacer kit. since the spacer kit included a lockring, everything was simple.

i am building up a second ss, again on a freehub, but this time the spacer kit doesnt include a lockring, and i dont have any spares.

i was looking to pick up a spare shimano cassette lockring at jenson or universal cycles, but not sure which to get.

will any shimano cassette lockring work? whats the difference between the 11t and 12t lockrings, and does it matter since i am not using a cassette anyway? and do i need to get a 9 speed lockring since the freehub is for 9 speed cassettes?

also, is it okay if i use a road bike cassette lockring? ive seen some cheap ultegra lockrings around. for that matter, does it have to be shimano? will sram or other brand lockrings work?

helps appreciated, thanks.