The smallest laser module has a diameter of 3.3 mm. It is a 650 nm dot laser - available in a plastic or a metal housing. In the plastic version, the maximum output power is less than 0.9 mW - a metallic version < 3 mW is available, too.
For larger diameters between 6.2 mm and 10.5 mm, wavelengths other than 650 nm are also available. In addition to the very brightly perceived red at 635 nm, there are also versions at 780 nm and 850 nm. Even focusable versions and line lasers are offered.
More Information: http://www.lasercomponents.com/...