This is an arm, you need two and a metal rod with diameter 6mm (one came with my printer) to hold the filament roll. It is for mounting upside down (from 'ceiling')

How I Designed This

Onshape: https://cad.onshape.com/documents/ef35264026cc7a653a5dd6ed/w/6beacf39d75916ef366e2b8b/e/9cf8772c8879b71083180223

Category: 3D Printer Accessories