paraffin (candle) wax. It's supposed to be the best and really doesn't attract dirt. I remove chain every 100km, pour hot water over it to clean it, but it really doesn't need this. When it's cold again it is stiff because there is still wax inside! 100km is very conservative. I don't ride in very wet conditions though - it's either very dusty (warmer months) or damp and a bit muddy. Before I used to have to clean and oil every 30km. This has saved me so much time. It's also very old school.