Threaded ring for E14 sockets with a 2 metric thread pitch. 
The ring has an internal diameter of 28.9 mm, for a ~28 mm diameter bulb socket.

You can also use this onshape model to tweak any dimensions: [https://cad.onshape.com/documents/3cf01824f3445e4c00b5030c/w/dd45d4b552000e9780c06af9/e/13c816e602dd8164cb6bc479?renderMode=0&uiState=69709f51bc950c09842a9ea6](https://cad.onshape.com/documents/3cf01824f3445e4c00b5030c/w/dd45d4b552000e9780c06af9/e/13c816e602dd8164cb6bc479?renderMode=0&uiState=69709f51bc950c09842a9ea6)