Stern Tanning CO calfskins are the BEST hides available. 
 
I have a limited supply of hides  - large enough to make 11 13/16" and 12" sizes. 
 
Stern tanning produces highest-grade, machine-sanded, calf hides. Stern hides feature precise, even, thickness (for optimum tonal response). These hides are .012 in. thick which is ideal - for high-grade calfskin - in my experience.  These are comparable to the best heads of the bygone era.
 
I recommend Stern Tanning co calfskin for bluegrass banjos and collectable vintage instruments. These heads have been supplied to numerous top professional pickers and for holy-grail pre-war instruments.  
 
NOTE: Stern hides are natural (unbleached). This is preferred because chemical whiteners may weaken the hide. Stern calfskins exhibit some degree of natural mottling and/or coloration. The photo is one example from my current stock.  Each hide is unique (the appearance will vary).
 
Stern calfskins may not be stained or oil finished. Wax treatment is included at no extra cost. SUPPLY IS VERY LIMITED.