Shakespeare 4700-2 24" Stainless Steel Extension Mast. Extend Antenna Height for Stronger, Clearer Marine Signals. The Shakespeare 4700-2 Extension Mast is a 24" (2 ft) stainless steel extension designed to raise the height of your marine antennas for better signal clarity and range. Ideal for clearing obstructions and improving line-of-sight, this rugged extension works with a variety of antenna types, including VHF, GPS, CB, and AIS. Built with durable stainless steel and standard 1"-14 thread