Joint Set are NOT usable alone.  

There are three different ring widths; 5mm, 8mm and 12mm available for the Flat Ring Set. Each basic set includes a part we call "joint" which sets the ring thickness to 2.0mm. Additional three thickness(1.5mm/2.5mm/3.0mm) are available by using separately sold Joint Sets.

They must be used with a 8 mm size 21 flat set.  PMC123's (#11) will work with this joint set.  

Ring Maker conversion Chart

Small  will make rings from size 4 ½ to 6 after firing (Japanese size 17)

Medium  will make rings from size 6 to 7 ½ after firing (Japanese size 21)

Large  will make rings from size 7 ¾ to 9 after firing (Japanese size 25)

Xtra Large  will make rings from size 9 ¼ to 10 ½ after firing (Japanese size 29)

 These are being closed out, hurry while supplies last!