ICBM stands for Integrated Cup and Bearing Module. It is a custom integrated headset produced by Schwinn for its bikes. The headset, for those who don't know, is the part that connects the steering assembly of a bike to the rest of the bike while allowing it to rotate freely. The purpose of an integrated headset it to reduce weight, increase strength and make the bike look better. The ICBM was introduced around 1998 on Schwinn's high-end bikes and was the first integrated headset on the market.