Simply a Mount AKA Holder with an ID of about 10mm to suit a 10mm LED or similar.
Threaded to suit a hole of 16mm so you can mount in a panel for use in applications like a pc case, car dashboard etc.
Upgraded version 2 (June 2019):
Slightly more lenient tolerances to make assembly easier
Added some chamfers for aesthetics
Added ramps to the nut to prevent loosening.
The author marked this model as their own original creation.