Stems

Stems are generally divided into two main types, which require different matching forks and headsets:

• Ahead™ stems clamp are compatible with threadless forks and headsets, they became increasingly common as the 1990s progressed and are now almost ubiquitous.
• Older quill stems clamp inside threaded forks and are compatible with threaded headsets, they are only really used on cheap or retro style bikes these days but are found on almost every bike pre-1990.