Features:
Aluminum anodized shaft
Metalic+White UV-Resistant thermoplastic socket base
Height adjustable: 49-76cm 19.5-30"
Swivel head, which can also set to be fixed
Specifically designed for marine applications and made with high quality materials for a long service life
Can be used for a boat, yacht, RV, etc.
Tough, water resistant design
Easy to install; 6 screws to set in place and 6 screws to attach to the seat. 
Seat can be easily removed from the base.
A table top with proper attachment (we also offer) can be mounted on this base since it is interchangeable.
Mounting screws are NOT included
Specs:
Dimensions:
Height: 19.53-29.84" (496-758mm)
Base diameter: 8.98" (228mm)
Weight: 6lb 15oz (3144gr)
Base mounting holes on center: 
3.94" (100mm) holes next to each other
7.85 (199mm) holes across from each other
Base mounting holes 8.44mm
Seat mounting bracket: 6.93x6.93" (176x176mm)
Seat mounting holes on center: Adjustable due to slatted design. Please refer to photos.
5.04-6.06" (128-154mm) holes next to each other
6.81-8.66" (173-220mm) holes across from each other