my current cog

was from my old 7-speed Shimano casette. I've found that an 18t rear cog is what I'm comfortable with.

The problem is long term wear. Being made of aluminum, this is quite "soft" for something that'll see a lot of use. So, one of my LONG TERM upgrades is the following:

Boone Titanium cogs and chainrings

They look real trick, and should last longer than what I have now. Boone also makes rings (as in for your fingers) out of the preciousmetal.

Hmmm. One gear to rule them all.