It will hold your backbox in place in case you are using propene foam to mount the box.

its made to fit on this stick: https://tesi.si/izpostavljeni_produkti/novo/4445/teleskopska_podporna_palica_115_290_cm_30_kg/

ball on the head is 20mm.

i used m5 abd bolts to scre the joints together. to eazily tighten then bolt i used bolt head from here: https://www.thingiverse.com/thing:2194278