The Area 419 Funnel’s interchangeable heads thread onto the funnel and are neck-diameter specific for each caliber. They do not rely on fitting over the body of the case to hold in place. They are sized slightly larger than the neck diameter so that they hold solid on the case. Each head has a bore sized a few thousandths smaller than the bullet diameter, so maximum flow is achieved for each caliber. This is huge for the super ultra magnum guys (375 Cheytac, 408 Cheytac, 50 BMG, etc). The interface between the heads and the funnel is designed in such a way that no kernels can ever get stuck between the two, as long as the head is tightened completely. The Funnel’s design is both aesthetic and performance driven. Being machined from a solid billet of 6061-T6 aluminum means no static charge to cling kernels to the funnel walls. This also makes it far safer for use with black powder.