MIL-P-21929
Military Specification, Plastic Material, Cellular Polyurethane, Foam-in-Place, Rigid (2 Pounds per Cubic Foot)
Published by U.S. Department of Defense (military specifications) (DoD)
The CFR incorporates MIL-P-21929 by reference, which makes the edition it names part of the regulation. The CFR requires the edition it names, which may not be the newest. To enforce any other edition, the agency must publish the change in the Federal Register.
The 4 editions the CFR requires
Different parts name different editions; each applies where its part says so. Newest first.
MIL-P-21929B, 15 January 1991
As the CFR lists it: “MIL-P-21929B, Military Specification, Plastic Material, Cellular Polyurethane, Foam-in-Place, Rigid (2 Pounds per Cubic Foot), 15 January 1991”
- Listed in 46 CFR 170.015(c)(1); required by46 CFR 170.245 ↗
MIL-P-21929C, 1991
As the CFR lists it: “Military Specification MIL-P-21929C, Plastic Material, Cellular Polyurethane, Foam-in-Place, Rigid (2 and 4 pounds per cubic foot), 1991 (“NPFC MIL-P-21929C”)”
- Listed in 46 CFR 175.600(f)(1); required by46 CFR 179.240 ↗
MIL-P-21929B, 1970
As the CFR lists it: “MILSPEC-P-21929B Plastic Material, Cellular Polyurethane, Foam-In-Place, Rigid—1970”
- Listed in 33 CFR 183.5; required by33 CFR 183.516 ↗
MIL-P-21929B, August 11, 1969
As the CFR lists it: “MIL-P-21929B, Military Specification, Plastic Material, Cellular Polyurethane, Foam-In-Place, Rigid (2 and 4 Pounds per Cubic Foot), (August 11, 1969)”
- Listed in 46 CFR 160.010-1(d)(2); required by46 CFR 160.010-5 ↗
How to read it
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A free or purchased copy may not be the edition the CFR names; check it against the edition above. Every incorporated standard can also be inspected at the National Archives (NARA) and at the agency named in the section that lists it.
MIL-P-21929 is copyrighted by its publisher; RegKnot shows its title and the editions the CFR names, not its text. Read from the eCFR's incorporation-by-reference sections, current as of October 26, 2026. The regulation text governs. All standards the CFR requires.