Here in Canada, underwear, top and bottom is called "next of skin" and you are not required to return any issued item in that category. I noted this was a rare event with them, mediated by Covid shortages in their supply line and used underwear is cleaned and assessed for suitability for re-issue.
There is a maker in the USA, 'under armor', not related to army use, but it is a good rabbit hole for stuff I did not know...lol
<a href="https://en.wikipedia.org/wiki/Interceptor_Body_Armor" rel="nofollow">https://en.wikipedia.org/wiki/Interceptor_Body_Armor</a><p>and the Russian counterpart...<p><a href="https://en.wikipedia.org/wiki/Ratnik_(program)" rel="nofollow">https://en.wikipedia.org/wiki/Ratnik_(program)</a>