Reviewed by Timothy Dike
April 2015
3D printing is making it easier to bring new parts to market. 3D Model Parts is on a roll and one new release is their 20 mm twin with the light weight mount common on late war US Navy ships. 
 Safely packed in a clear tube is one wafer with 24 resin gun mounts attached. They are made in two parts; the gun base pedestal and the twin barrel gun assembly. It is made so the the barrels mount on the pivot point so you can display the gun at any realistic elevation.  They are printed in an orange colored flexible acrylic resin that is pretty strong.  Click images
to enlarge
Mp photos don't show it well due to the mono color look of the parts, but you have distinctive barrels, ammo cans, and shoulder braces.  The pedestal is filled and up close looks closer to the older solid pedestal mounts, but you can apply a dark wash on them to simulate the open tripod look. 
Below is a build up showing the four types of 20 mm gun mounts and the 20 mm twin shown installed.
Yes, there are finer options with PE gun sets, but not all modelers like working with fragile parts. These gun mounts cater to those who want more detail without the frustration of intricate PE.

This is #U703 1/700 Twin 20-mm Oerlikon Cannons - Tripod Mount -24 pcs for $5.95 US. You can double that to 48 pcs for only $4.00 more. They are available direct from 3D Model Parts.