Parts and equipment manufactured for use by the U.S. military and Department of Defense (DOD) must comply with stringent military specifications (Mil-Spec). Mil-Spec includes tight tolerances for dimensions of parts and the ability of equipment to withstand extreme ambient conditions in storage and in operation. Other requirements of Mil-Spec include the standardization of all materials and parts, use of unique identification (UID) labels, and stringent quality control in manufacturing. Mil-Spec guidelines require exacting standards for the following reasons:

• Harsh environments. The equipment must work flawlessly in dangerous situations, so it must be of higher quality than equipment used in similar civilian applications.
• Standardization across vendors. The military employs a large number of contractors to manufacture thousands, even millions, of pieces of the same equipment. It is crucial that there is uniformity among the parts and equipment supplied by different contractors.
• Rare materials. The operating conditions may demand the use of special metals and alloys due to high heat or other extreme environmental conditions.
• Large part volumes. The military industry is a very large sector that uses a wide variety of parts and equipment in large quantities. Sometimes these have to be supplied on little notice with short lead times.