OEM Visible Photon Counter is intended for large-volume OEM applications. It is the smallest, most reliable, and most efficient single-photon detector on the market, consisting of a CMOS (Complementary Metal Oxide Semiconductor) silicon chip packaged in a standard TO5-8pin header with a transparent window cap. The chip combines either a 20 μm (ID101-20) or a 50 μm diameter (ID101-50) single-photon avalanche diode and a fast active quenching circuit, which guarantees a deadtime of less than 50 ns. The chip is mounted on top of a single-stage thermoelectric cooler (TEC). Three fibre-coupled versions, the ID101-SMF20, the ID101-MMF50 and the ID101-MMF100 are also available. The maximum photon detection probability is measured in the blue spectral range (35% at 500 nm). An outstanding timing resolution of less than 60 ps allows high accuracy measurements. The performance of the ID101 detectors is comparable to that of the ID100-20 and ID100-50 modules. The ID101 can be mounted on a printed circuit board and integrated in apparatuses such as spectrometers or microscopes. The module is used in biological/chemical instrumentation, quantum optics, aerospace, and defence applications. ID101 detector is fabricated using a qualified commercial CMOS process, which guarantees high reliability.