The Honeywell SD3421/5421 series consists of PIN photodiodes designed for use in TO-46 metal can packages. The SD3421 utilizes a flat window, providing a wide acceptance angle, while the SD5421 employs a glass lensed can for a narrower acceptance angle. These photodiodes are suitable for operation in harsh environments and are mechanically and spectrally matched to Honeywell's SE3450/5450, SE3455/5455, and SE3470/5470 infrared emitting diodes. They find applications in various industrial and commercial settings where reliable light detection is required.