Bike stems come in a variety of lengths, angles, steerer clamp diameters (1", 1 1/8" (28.6mm) or 1 1/4" (31.8mm) and handlebar clamp diameters (25.4mm, 31.8mm and 35mm).
Modern MTB stems commonly come in 1 1/8" steerer clamp. The handlebar clamp is either 31.8mm or 35mm. However, in recent years many mid and long-travel bikes use the 35mm clamp for extra stiffness.
