"The *fabled* Gold Medal Pro track cog" - 1/8" chain compatible only.
"For professional track racers. Perfect threads, roundness, concentricity, and tooth profiles. Titanium Nitride coating increases lubricity and durability. Ridden by the most dominant track team in the world. With wins in the World Championships plus the Beijing and London Olympics, this cog is appropriately named."
- EAI
As you can obviously see, the Gold Medal Pro is the finest track cog money can buy. Made in the USA and filed and painted by hand. This cog is the ultimate flex!