Sensors turn a physical quantity into a signal, and that signal depends on the parts around it: a housing that moves, a sealing face that leaks or a bore that is not round will all show up as measurement error.
Sensor housings and bodies, mounting and sealing plates, diaphragms seats, connector blocks and adapters.
Stainless steel and titanium for corrosion and strength; Kovar where a glass or ceramic feedthrough must be sealed in; PEEK, PVDF and PTFE where chemical resistance or dielectric properties dominate.