An adapter for inserting into a carton containing a non-reel coil of filamentary material or wire has a shaft-receiving sleeve supported by a box structure. The adapter's structure has top, front, bottom and back walls reinforced by side gussets. The underside of the top wall, the interior of the back wall, and the top of the bottom wall of the adapter define a channel. The channel is oriented such that it may receive a shaft or rod of a wire pulling rack. The adapter may be assembled from a blank of foldable material. The adapter blank may be manufactured as a detachable element of a carton blank which is also used to construct a carton to hold a non-reel coil of filamentary material.