skip the Park ones, get a Hozan, either the spanner or the pliers. Park sucks. Period.
From BusinessCycles' site:
http://businesscycles.com/trpart.htm#lockring
Hozan C-205 lockring spanner - double-ended (different radii) single-tooth lockring tool - $22.50
Hozan C-203 lockring pliers - For applications where some grunt is necessary - $36.50.