The Phil cogs have a nicer, cleaner threading than anything else I've seen, including EAI's. This means they don't abrade your hub threading as much as other cogs, which is a good thing. They have a shape and a finish that are quiet as cogs go, which may not have practical value but is nice to have. And their stainless alloy means they don't develop little rust blooms in the rain the way an EAI cog does, but this is also of limited practical value -- an EAI cog is way too stout to be done in by superficial rust. The biggest issue, and the one that really justifies them to me, is the quality of the threading. Just read this forum for a while about cogs, and what's the number one complaint? It's about bad threading or stripped threads, right? If you have a cog that saves your hub, isn't that a major step forward?

The only problem with Phil cogs has been their spotty availability. For a while there were 16, 17 and 18 tooth cogs, then some 15's, now there are 14's but some of the earlier sizes are now in short supply. Each cog gets hand-polishing which may be limiting their production volume. Whatever, it's a very nice cog.