Springfield Plug-In 9" Round Hi-Lo Base f/2-3/8" Post

The Springfield Plug-In 9" Round Hi-Lo Base for 2-3/8" Post is a below-deck marine mounting solution engineered for stability and durability in demanding vessel environments. This base serves as the foundation for antenna masts, outriggers, and other topside equipment requiring secure, vibration-resistant mounting on recreational and commercial watercraft. Law enforcement and military maritime units rely on this class of hardware to maintain structural integrity under operational stress, making it essential infrastructure for vessel systems that demand unwavering reliability.

Manufactured from high-strength aluminum with a satin finish, the Springfield base features a 9-inch round profile with an 8-inch bolt circle hole pattern, accommodating standard marine stud configurations. The design utilizes a below-deck mounting approach, requiring a 3-3/4-inch diameter hole cut into the vessel deck for installation. This hi-lo base geometry distributes loads across a wider footprint than conventional single-height bases, reducing point stress and extending service life in saltwater and freshwater conditions. At 2.25 pounds, the base remains lightweight while maintaining the structural properties necessary to resist corrosion, flexing, and fatigue from wave action and equipment vibration.

This base pairs exclusively with any Springfield 2-3/8-inch plug-in post system (sold separately), making it compatible with a wide range of mast extensions and antenna configurations across the Springfield Marine product line. Installation requires standard marine fastening practices and a properly sized deck penetration; the below-deck mounting method provides superior weather sealing and aesthetic finish compared to surface-mount alternatives. Boatyard professionals and DIY builders working on renovation or new-build projects should verify deck thickness and material composition before cutting mounting holes. The compact 10 x 4 x 11-inch footprint accommodates space-constrained deck layouts without sacrificing load capacity.