A
cylinder is the central working part of a
reciprocating engine or
pump, the space in which a
piston travels. Multiple cylinders are commonly arranged side by side in a bank, or
engine block, which is typically
cast from
aluminum or
cast iron before receiving precision machine work. Cylinders may be
sleeved (
lined with a harder
metal) or
sleeveless (with a wear-resistant coating such as
Nikasil). A sleeveless engine may also be referred to as a "patent-bore engine".