Spool adapter insert for ABC Plastics spool model MC-008W, which is used by many popular filament brands:

COEX
Fusion Filaments
IC3D
Jessie Filaments (Printed Solid)
Makeshaper
Marlon Precision 3D Filament
Matter Hackers
Push Plastic
Toner Plastics

The MC-008W spool has a recessed portion of the arbor hole that allows the spool to attach to winding machines. This recess prevents the spool from being symmetrical and can cause the spool to slide off the AMS lite during printing when the recessed side of the spool is mounted on one the AMS lite rotary spool holders where the inside of the arbor hole won't make contact with the friction pads on the AMS lite rotary spool holder.

This adapter locks into the spool's arbor hole and fills the recessed area, which provides the necessary surface contact and friction for the AMS lite rotary spool holders to function properly and retain the spool on the AMS lite system during operation.