Ink Sacs £2.55 Ink Sac Size: [Choose]Size 12Size 14Size 15Size 16Size 17Size 18Size 20Size 22 Quantity: at £2.55 each Add To Basket Latex Ink Sacs See size guide below to choose the right sac for your pen. Size Inside Diameter Outside Diameter Section Nipple Range Internal Barrel Diameter 12 3.76mm 4.76mm 3.8mm - 4.6mm >5.5mm 14 4.56mm 5.56mm 4.6mm - 5.0mm >6.5mm 15 4.95mm 5.95mm 5.0mm - 5.4mm >7.0mm 16 5.35mm 6.35mm 5.4mm - 5.8mm >7.5mm 17 5.75mm 7.75mm 5.8mm - 6.2mm >8.0mm 18 6.14mm 7.41mm 6.2mm - 7.0mm >8.5mm 20 6.94mm 7.94mm 7.0mm - 7.8mm >9.0mm 22 7.73mm 8.73mm 7.8mm - 8.6mm >10.0mm If there is a conflict, use the sac which will fit the barrel most comfortably. In addition, the following list gives a number of the most common pens and their associated ink sacs; Parker: Duofold Senior - 20Junior / Special - 16Lady - 15Duofold AF - 17Victory - 17 Wahl Eversharp:Skyline - 17#2 - 15 Watermans: Crusader - 18W3 - 1732V - 1752 - 1855 - 20502 - 16Commando - 17W5 - 18 Swan (Mabie Todd): 31xx - 1632xx - 1744xx - 2046xx - 22SM100/60 - 172-SF - 18L212-60 - 18Minor - 16 Conway Stewart:No.106 - 16 No. 12 - 17No.15, 28, 84, 388, 356, 475, 759 - 18 No.55, 58, 60, 60L, 286 - 20 Length is 75mm, cut to length as required. Fix with Shellac, available here.