This Listing is for Brand New Set of 10 High Quality Large Capacity (M Size) Aluminum Bobbins for Handi Quilter HQ16 HQ18 A-1 QUILTER, Gammill QUILTERS.
This "M style" bobbins measure 1" in diameter and 3/8" thick. Aluminum bobbins are considered the Top-End "Luxury Bobbins". They offer less resistance which translates to less drag to the bobbin thread tension.
These bobbins do not have winder slot.
The ones with winder slots are listed here:
http://www.ebay.com/itm/10-GAMMILL-TIN-LIZZIE-QUILTER-M-LARGE-ALUMINUM-BOBBINS-HOLES-/320957654908?hash=item4aba91277c