This silica gel dessicant holder is designed to fit in the spool center hole onmost filament brand. The holder has a center rod to reduce the volume of silica gel, as those in the middle are less effective.
The model uses a twist lock design instead of screw thread to avoid the need of support.
Best to print out of PETG. With PETG it's possible to throw the entire holder into a 70C oven to reactivate the silica gel.