This is a remix on another user's model of a magnet attachment for the back of the X1/P1 Printer. It allows a bag to be attached to collect waste filament. It needs 4x 6mm x 5mm Magnets. I purchased these:

https://www.amazon.com/dp/B07KLV4D3D?psc=1&ref=ppx_yo2ov_dt_b_product_details

The original poster is here: https://makerworld.com/en/models/69042#profileId-73280