an oximeter sensor formed with a housing made of a relatively rigid material into which the oximeter electrical components can be mounted is provided . an overmolded material , of lesser rigidity , is injection - molded over the housing to complete the sensor . in one embodiment the housing is made of plastic , such as polypropylene , and the overmolded material is an injection - molded thermal plastic elastomer , such as santoprene ™ . the housing preferably contains thin portions connecting thicker portions which support the electrical and optical components . these thin portions provide natural bending portions in the final oximeter sensor . by having the thin portions near or at the central , neutral axis of the sensor , flexibility is optimized in the longitudinal direction , while the housing provides stiffness laterally .