Those are insulators for mounting the wire on outside off MP-48
You have to a loop in the wire so that the MP-48 can bend and not strech the antena wire
I have Military and Radio Surplus.
MVPA Life Member 683
1943 GPW 98356, 1964 M151, and trailers, plus many Radio's 916-761-5293
Seabee Navy 1982-1988
NRA life Member, KE6EMX
Sold M35A2, M38, M38A1, M880 M37B1 all restored by me