The M6-12BWZ is a white zinc coated metal bolt that its only purpose is to assemble the HJ-15NP joint. To assemble an HJ-15 joint, you need to connect one H-15NP and one H-16NP with one M6-N nut and one M6-12BWZ bolt.
This bolt is fixed to the M-6N using a 5mm T-HANDLE allen wrench. (It is essential that the bolt is tightened between 12-14 N.m torque.)
A Flexpipe Product
For technical details and images, please search for the product using the 80/20 interactive catalogue found here: https://catalogs.8020.net/80-20-Catalog-26/C/.