I have the 4th element dry base which is the two piece pant and shirt and . I have test dove the BZ on multiple dives as well as Halo 3d - I. Concise drysuit undergarments reviews tailored to your needs. Because we believe the best drysuit undergarment is not the best for everyone. Undersuit Fourth Element HALO 3D. Appeared in DIVER January THE ' WOOLLY BEAR' used to be standard issue for use with drysuits. It was an. Next solution the 4th element Halo 3D . no problems staying warm, dumping gas or big weighting issues and stood the test of time for me. Halo 3D Undergarment by Fourth Element I was recently given a chance to take the new Halo 3D undergarment out for a test dive. Our friends. HALO 3D. ADVANCED TECHNOLOGY THERMAL UNDERSUIT. Our warmest undergarment, equivalent to a g thinsulate with less bulk due to body- mapped. This is Fourth Elements newest undersuit. Designed to maximise thermal protection and minimise buoyancy, the HALO 3D has body mapped insulation placed.