A mouse is mostly air inside an ABS shell. The parts that determine how it feels — the switches, the encoder, and the feet — together account for a small fraction of its weight and most of its perceived quality.
7 parts — 3 you can see, 4 you can’t without opening it.
ABS, sometimes with a rubberised or soft-touch coating
ABS moulds crisply, takes texture well, and is stiff enough at thin wall sections. The soft-touch coating is the part that degrades — it hydrolyses into a sticky film after a few years.
Sealed micro-switch: a steel leaf spring and gold-plated contacts in a polymer housing
The leaf spring's shape produces the click and the tactile break. Gold plating resists the oxide film that causes double-clicking as switches age.
Silicon imaging die, an IR or laser LED, and a moulded plastic lens
The sensor photographs the surface thousands of times per second and compares frames. The lens sets the focal distance, which is why lift-off behaviour differs between mice.
Mechanical rotary encoder with a metal detent spring, or an optical wheel
The detent spring makes the notches you feel. Mechanical encoders wear and start to register phantom scrolls; optical ones don't, but cost more.
FR-4 fibreglass with copper traces, lead-free solder
FR-4 is the default because it's dimensionally stable and cheap. There is nothing exotic here in almost any mouse.
Virgin PTFE, occasionally glass-filled or ceramic
PTFE has an extremely low coefficient of friction against most desk surfaces. This tiny part determines most of how the mouse feels to move.
Stranded copper in PVC, or a braided nylon sleeve
Braiding is mostly cosmetic and can add drag; the flexibility comes from the strand count and the jacket compound, not the sleeve.
Weight is now a design decision rather than a consequence. Lightweight mice remove shell material rather than change it, which is why a 50 g mouse and a 100 g mouse are often the same polymer.
Switches are through-hole soldered and genuinely replaceable if you can desolder — this is the single most common and most worthwhile mouse repair. Feet peel off and are sold as spares. Sensors and encoders are surface-mounted and effectively not user-serviceable.
This page describes the category. Exploded reads the specific object in front of you — photograph your computer mouse and get a breakdown of its parts, with every guess labelled as a guess, then explore what could be built differently.
Analyze your computer mouse