Pen Sac - Size 20 Straight. 20/64 inch diameter latex pen sac, a popular larger size used in Sheaffer, Waterman, Parker, Eversharp, Conklin and other fountain pens.

Pen Sac - Size 18 Straight. 18/64 inch diameter latex pen sac, a popular larger size used in Sheaffer, Waterman, Conklin and many other fountain pens.

Pen Sac - Size 16 Tapered. 16/64 inch diameter tapered latex pen sac for Eversharp Skyline fountain pens

Pen Sac - Size 16 Straight. 16/64 inch diameter latex pen sac (one of the most popular sizes) for many fountain pens, including Esterbrook, Sheaffer, Parker, Waterman and others.

Pen Sac - Size 14 Straight. 14/64 inch diameter latex pen sac for Sheaffer Snorkels and smaller fountain pens. While totally non-pen related, the smaller sized sacs, usually #10, #12 and #14 are used by model airplane enthusiasts for fuel tanks!