The Outbacker Extra Heavy Duty HF mobile antenna Spring Mount, is  maufactured in 316 marine grade stainless steel, machined and produced in house. The spring is wound from 8mm gauge, 304 stainless steel wire with welded, not pressed 316 stainless steel ferrules. Ferrules and spring are stainless steel and don't rust, as other brands do on salt affected roads and highways.
Feed connection via an SO239 socket. NOW field replaceable.
Suitable for mobile use  with antenna's  up to 3.0m tall. 
Sprcifications:-
OBASMSS  Spring & Mount. $250.00 (aud).
Thread size, spring to antenna 3/8x24unf female.
OBAMSS     Mount Only.         $190.00 (aud). 
Thread size to, antenna 3/8x24 unf male.
Thread size to, vehicle 12mmx .75 metric.
OBASSS      Spring Only (all stainless steeel $127.00 (aud). 
Top & bottom thread size 3/8x24 unf female.