This is a “heavy” collar that can be locked with an integrated lock similar as those found in chastity cages.
For now the available model allows to put a steel ring in front (40mm inside diameter) and has a size of 120mm by 140mm (more than enough for a neck circumference of 38cm) and is 50mm high
You need a M4x50 screw to attach the two part and a lock
There is two version:
If you need a size I may create it.
The author marked this model as their own original creation.