The stud mount is an essential component for most two-way radio antenna installations as it is the component that accepts the antenna on the top side and the coaxial cable on the bottom side (in most cases). There are some mounts that do not require a stud mount but those are less popular than the majority of common antenna mounts.
All common antenna stud mounts are designed to be mounted in the industry standard half-inch hole (0.5" or 12.5mm). The type of stud mount you choose needs to match the type of coxial cable termination you intend on using.
With the exception of no-ground-plane (NGP) antenna systems, at least one component of the stud mount or coaxial cable must be grounded so, if installing on a powder coated, annodized or other surface that is insulated from a vehicles chassis ground, work must be done to remove powder coating or annodizing from the surface that the stud mound or coaxial cable is required to have contact with chassis ground. Before the coaxial cable is connected to the radio, the ground path must be confirmed. You cannot rely on any ground path that has to come from the radio itself. Missing or poor ground paths will always result in unsatisfactory standing wave ratio (SWR).
The following graphic depiction of the three popular stud mounts should help you understand how the various stud mounts attach to the mounting surface/bracket and what matching coaxial cable termination is required.
Updated Oct. 20, 2015