Frames equipped with the original Mission Control integrated headset (2” diameter bearings top & bottom) can be converted for use with standard 1 1/8” forks with the assistance of Problem Solvers 1 1/8” reducer kit (QBP # HD9903) available at most Klein dealers.
Reset, a specialty component manufacturer from Germany also offers a reducing system that takes the place of the original headset bearings (Reset # 1114). 1989 to 1993 Attitude, Adroit and 
Adept models are compatible with this system.
Frames equipped with MC2 or MC3 AirHeadsets (2” diameter lower bearing, 1.75” upper bearing diameter) can be converted for use with standard 1 1/8” forks with the assistance of the Reset 1 1/8” reducer kit (Reset # 1114-1). 1994 to 1999 Attitude and Adroit models are compatible with this system.
Reset also produces a 1 1/8” reducer kit for second generation MC3 (MC3.1) equipped frames (Reset # 1114-2). 1999 and after Mantra Race and Pro as well as 1999 and after Adroit Race Pro are compatible with this system.
You may opt to use a different handlebar/stem combination with the reducer kits mentioned, however Reset also offers an adapter that allows for continued use of the original (Reset # 1114-3).
Reset tel. 49-0-511-924-54-29
www.reset-racing.com