Mast AB-621 was developed as part of the ANGRC-67 Radio Terminal and ANGRC-68 Radio Repeater. It was type classified Std-A in Augugst 1964, and is used with the ANGRC-144 Radio Set in the Army Tactical COMMUNICATIONS High Capacity Subsystem. The AB-621 is a quickly erectable, uniformly sectionalized, guyed mast which can be erected to heights of up to 50 feet. It supports a 4.5 foot hornfed parabolic reflector antenna. Previous arctic testing of similar masts AB-577 and AB-952 revealed a safety deficiency in that the accumulation of frost, ice and snow on the exposed portions of the masts prohibited safe disassembly. To preclude the occurrence of similar problems during arctic service testing of the Mast AB-621, a winterization kit for the mast was developed. The winterization kit consists of protective mast section covers, guy snubber covers, rubber shrouds to protect the launcher assembly, an expendable plywood base and the necessary auxiliary tools needed to install the kit on the mast.