Seiler Instrument is a contract manufacturer of specialized fire-control equipment and a distributor of surveying instruments, microscopes and other optical equipment.

The manufacturing division specializes in precision optical instruments and components, focusing optical fire-control equipment. Customers for this equipment include the U.S. Military and international customers, notably Canada. Products include periscopes, telescopes, target collimators, boresights, borescopes, gunsights, dioptometers and tripods. Its product portfolio comprises over 50 different equipment types, as well as the variants of each. Resources include CNC machining, turning, optical/mechanical assembly and a full testing and inspection capability to MIL-I-45208 and MIL-Q-9858.

Seiler Instrument also manufactures a family of test fixtures for the production, calibration, and repair of fire control systems. They are built for internal use, and for sale to government and industry customers. Seiler manufactures to U.S. Government designs, but has also developed retrofit packages to digitize the fixtures. The resulting angle encoders achieve better than 1/10 artillery mil (1/64000 of a circle) accuracy, and greatly reduce setup times. They can be delivered as complete test fixtures, or for retrofit to existing equipment.

Notable Seiler glass and iron sights are used on Canadian weapon systems from the LG-1 (GIAAT) & M-777 (BAE) and legacy systems such as the C1 & C2 howitzers.

Seiler Instruments is also partners in Tactical Optical Solutions Inc. another company that is owned by Mr. March who also owns Kaycom Inc. This company does complete repair and overhaul and is under contract with the Canadian Military.

Seiler's headquarters are in St. Louis, Missouri, United States.

Kaycom is Seiler's exclusive Representative/Distributor for Canada and Thailand.