specification, military standard (MIL-STD) is a United States Defense
standard used to describe a product that meets specific performance and
manufacturing standards for equipment and chemicals.
Other non-defense government
organizations, technical organizations and industry may also use
military specifications are not just limited to The Department of
Defense, as other government organizations and Industry use them as
Here is a Q&A from the Department of
What is a performance spec?
A performance specification states requirements in terms of the
required results with criteria for verifying compliance, but
without stating the methods for achieving the required results.
A performance specification defines the functional requirements
for the item, the environment in which it must operate, and
interface and interchangeability characteristics.
Q. What guidance have we given on how to write a performance
A. Writing performance specifications is not a new concept. We have
been teaching how to write performance requirements for years at
our specification training course. It has received extra
emphasis in our training on how to write Commercial Item
Descriptions. What is new is that we are now designating
documents as "performance specifications."
Q. If you have a performance spec that is MILSPEC, is a waiver needed?
Q. Is it possible for a general specification to be designated as
performance and its associated specification sheets to be
designated as detail?
A. No. Since a general specification must be used together with a
specification sheet, the fact that the specification sheet is
detail requires the general specification also to be designated
Q. Within the same family of specification sheets, is it possible for some
to be designated as detail and others to be performance?
A. Generally, no. The decision whether to convert a family of
specification sheets to performance specifications must be
consistent across-the-board. In some cases, however, the number
of specification sheets that must be converted to performance
specifications may be very large, making it difficult to convert
all of them at one time. In this situation, there may be a
temporary blend of detail and performance specification sheets
within the same document number series. This situation is
acceptable as long as the goal is to convert all of them to
Q. Can a performance spec ever cite a detail spec as a requirement?
A. The citing of a detail spec as a requirement does not
automatically mean that a spec is not performance, but it is a
strong indicator that as spec may not be performance.
Performance specs should not cite any detail spec as a
requirement if it demands a specific design solution. But
performance specs may cite a detail spec if it relates to a
physical or operational interface requirement.
For example, it would be permissible to have a requirement in a performance engine
specification that required the engine to operate with specific
substances, such as lubricating oil or fuel, which conform to
detail specs. The requirement that the engine be able to operate
on a specific type of fuel is an operational interface
requirement and does not dictate the specific design of the
engine. However, it would not be permissible in a performance
spec to require the engine be made of certain materials or that
the various engine components conform to detail specs since such
requirements would dictate specific design solutions instead of
stating the performance expected.
Q. I'm writing a spec that describes a "kit."
it be a detail (MIL-DTL-) or a performance (MIL-PRF-)
A. In general, the answer is that it will likely be a detail
specification; however, there can be exceptions. A spec for a
kit describes a collection of related items, such as adapters,
couplings, bags, tools, attachments, or accessories. A kit may
contain items for installing, testing, or starting up a system
or piece of equipment; it may be provided to equip an existing
system for specific functions; or it may be used to adapt
equipment to meet new or specialized conditions. If the spec
writer were careful to write all of the requirements for the
kit's contents in terms of form, fit, function, and interfaces,
and to cite only performance-type documents, the resulting spec
would support a MIL-PRF designation. As is frequently the case,
however, if one or more of the kit's components are described
using a specific design solution, Technical Data Package, MIL-DTL
type spec, or a non-government standard that contains detail
design requirements, the kit spec must be designated as a MIL-DTL.
The spec writer needs to keep in mind that all of the
requirements for all of the kits' components must be stated in
performance terms in order to produce a MIL-PRF.