W2DU Baluns use a ferrite sleeve to choke RF current on the cable shield! The W2DU Maxi-Baluns owe their extremely high power capability to the fact that they contain no ferrite cores to saturate. Even at high SWR levels, the W2DU Baluns won’t generate harmonic radiation. The internal feed line passes through ferrite beads which prevent RF current from flowing on the coax shield. Two 50 ohm 1:1 models are available; HF (1.8-30 mHz) and VHF (30-300 mHz). Operates at HF (1.8-30MHz). At 10 mHz, the HF model handles over 10 KW PEP at VSWRs up to 2:1. Each W2DU Balun has a built-in lightning arrestor, hang up hook, and 600 lbs of pull-apart strength in a weatherized, rugged package using only stainless steel hardware.