MFJ-4603 Window feedthrough panel SO239 BAL WIR N MFJ Weather-Proof Antenna Feedthrough Panels mounts in your window sill. They let you bring all your antenna connections into your hamshack without drilling holes through walls. Feedthrough Panel mounted to " x 3 " x 48" Western Red Cedar Plank. The customer cuts it down to their preferred size. The minimum would be 15 inches because the plate is at that point. Real Western Red Cedar wood is naturally resistant to rot, decay and insects -- lasts longer, maintenance-free. Pitch and resin free for a wide range of beautiful finishes or leave it in its naturally beautiful raw finish.f Simply place in window sill and close window. Edges sealed by weather-stripping. Seals and insulates against all weather conditions. Gives years of trouble-free service. Inside/outside stainless steel plates bond all coax shields together to ground connection. Stainless steel ground post brings outside ground connection inside.