New, *B Quality, 14mm Female-14mm Male Glass Ground Joint Attachment  Angle Conversion/Adapter/Connector. Made by Subconscious Design in USA. 

Similar to the item shown, see pictures for details.

*These are sold at a discounted price because they may have some cosmetic imperfections.

*Not made to hold heavy attachments. If you insist on using something heavy with this, adapt the angle on the other side of the heavy piece to avoid strain.

I'd recommend using a clip with an attachment like this to add stability. I have 14mm keck clips available here:

https://www.ebay.com/itm/324902018663