Fountain Pen Sac Size Guide

(This page revised December 18, 2017)

The charts on this page are a guide to choosing appropriate sac sizes for various sac-filling pens. The sizes listed here are not the sizes the original manufacturers used. Pen manufacturers chose the largest sacs they could cram into their pens in order to yield the greatest possible ink capacity, but there are some drawbacks to that method:

  • A larger sac is more difficult to insert into the barrel. Even if coated with talcum powder, it can bind against the barrel wall or the pressure bar, and it can twist and crinkle as the repairer tries to stuff it all the way in.
  • Because modern repairers are dealing with used pens, pressure bars can be distorted and there can be buildup on the surface of the pressure bar or barrel wall. These conditions make it even more difficult to fit a sac of the original size.
  • Because more of its surface is in contact with the barrel wall, a larger sac absorbs heat from the user’s hand more readily than will a smaller sac. This causes any air in the sac to expand, increasing the pen’s flow unpredictably and possibly causing the pen to blot, especially when it is nearly empty.

For these reasons, the charts recommend sacs that are usually one or two sizes smaller than the sizes originally used; but in some cases, the difference can be as great as four sizes. In most cases, the smaller sac size vitiates the need for a necked sac; unless otherwise specified, all sacs listed here are straight sacs. For pens not listed, choose a sac that drops freely into the barrel with the pressure bar in place.

If you do not see your pen listed in the chart, you can always measure to establish sac size. Measure the diameter of the section nipple where the sac attaches with callipers. Next conver the decimal size to the nearest 64th. fraction. For example 0.2344 is 15/64ths. this would be the largest sac size possible for your pen. You then must take into consideration the available clearence in the pen barrel. Replacement button and J bars can easily reduce the size of the sac by two sizes.

Despite the fact that latex sacs do not last forever and will need to be replaced, I still recommend them as the best available alternative. Do not use PVC sacs, which will bond themselves chemically to the barrel wall of many pens. I also dislike silicone sacs; they will not leak ink, but they are gas permeable and will allow air to pass into them such that the pen will leak ink through the nib and feed if it is stored horizontally or nib downward.

Note: If you are using a modern two-piece replacement pressure bar (illustrated here), choose a sac one or two sizes smaller than indicated in the chart.

Replacement Pressure Bars

Please follow this link for a complete list of available sacs and diaphragms.
In the tables on this page, necked sacs are indicated by the letter N, tapered sacs by the letter T.
Chilton Pens
Pen Model(s) Sac Size
Chiltonian 18
Golden Quill 18
Wing-flow (standard girth) 18
Conklin Pens
Pen Model(s) Sac Size
Duragraph (lever filler) 21
Endura (slender girth) 17
Endura (standard girth) 21
Glider (slender girth) 15
Glider (standard girth) 17
Symetrik (standard girth) 17
2NL, 2P, 20, 20P Crescent-Filler 17
25P Crescent-Filler 15
3NL, 3P, 30, 30P Crescent-Filler 17
4NL, 4P, 40, 40P Crescent-Filler 18
4NL, 4P, 40, 40P Crescent-Filler 20
6NL, 60 Crescent-Filler 21
75 Crescent-Filler 22
Esterbrook Pens
Pen Model(s) Sac Size
C, CH (J-series “purse” pens) 16
Deluxe (SM, LK) 16
Dollar Pen Size B (standard girth) 18
Dollar Pen Sizes A and H (slender girth) 16
J, LJ, SJ 16
M2 (squeeze filler) 16
Safari (lever filler) 16
Safari Plunger-Fill Ink-Vue (full size)
Chas. H. Ingersoll Pens
Pen Model(s) Sac Size
Bakelite twist filler 20
Metal twist filler 22
Moore Hard Rubber Pens
Pen Model(s) Sac Size
82, L-82 13
83, L-83 14
84, L-84 15
85, L-85 17
86, L-86 20
92, L-92 13
93, L-93 14
94, L-94 15
95, L-95 17
96, L-96 20
Moore Celluloid Pens
Pen Model(s) Sac Size
Finger tip (96-B) 17
82, L-82 14
83, L-83 15
84, L-84 16
85, L-85 18
86, L-86 22
92, 92-A, L-92 15
93, L-93 15
94, 94-A, L-94 16
95, L-95 18
96, 96-A, L-96 20
Parker Pens
Pen Model(s) Sac Size
Duette Jr. “Thrift Time” 15
Duette Sr. “Thrift Time” 17
Duofold Geometric (“Toothbrush”), slender girth 15
Duofold Geometric (“Toothbrush”), standard girth 17
Duofold Jr., Duofold Special 16
Duofold, Lady 15
Duofold Senior 19
Duofold, Striped, Junior (button-filler) 16
Jack-Knife Safety 20, 201/2 15
Jack-Knife Safety 23, 231/2 15
Jack-Knife Safety 26, 261/2 19
Moderne “Thrift Time” (Canadian) 15
Parkette Zephyr 14
Pastel (larger size) 15
Pastel (smaller size) 12
Premier “Thrift Time” (Canadian) 17
Raven 15
True Blue 15
Vacumatic Junior, standard girth (Lockdown) Standard Diaphragm
Standard Diaphragm  
Vacumatic Oversize (Lockdown) Oversize Diaphragm
Vacumatic Senior Maxima (Speedline) Oversize Diaphragm
Vacumatic Standard (Lockdown) Standard Diaphragm
All Vacumatic-filling pens not listed Deb Diaphragm
VS 16
“51” Aero-metric Demi/Slender See note below[1]
“51” Aero-metric Standard Pli-Glass
Sheaffer Pens
Pen Model(s) Sac Size
Autograph (postwar, largest size) 19
Balance (oversize) 20
Balance (slender girth) 15
Balance (standard girth) 17
Fineline 17
Lifetime Flat-Top (celluloid, slender girth) 15
Lifetime Flat-Top (celluloid, standard girth) 16
Lifetime Flat-Top (celluloid, oversize) 20
PFM 171/2×21/8 N
Snorkel 14×21/4 N
Touchdown TM 15×21/8 N[2]
Touchdown (1949 “fat”) 171/2×17/8 N
5-30 (standard girth) 17
7-30 19
22 Student Special 14
46 Special (slender girth) 14
46 Special (standard girth) 16
Wahl-Eversharp Pens
Pen Model(s) Sac Size
Coronet 16
Doric (slender girth); includes Doric Junior 15
Doric (standard girth); includes Popular DoricFifth Avenue 17
Fifth Avenue 16
Metal pens, Nº 2 nib (ringtop, 33/4" long) 15
Metal pens, Nº 3 nib (clip or ringtop, 43/8" long) 16
Metal pens, Nº 4 nib (clip, 5" long) 19
Metal pens, Nº 5 nib (clip, 47/8" long) 20
Personal Point (oversize) 20
Personal Point (slender girth) 16
Personal Point (standard girth) 18
Sixty Four 16
Skyline Demi 161/2×21/4 NT
Skyline Executive 18
Skyline Standard 161/2×21/4 NT
Slim Ventura (squeeze filler) 15
Symphony, 1st generation (Loewy) 151/2×23/4 NT
Symphony, 2d & 3d generations 17
Ventura 16
Waterman Hard Rubber Pens
Note: overlay pens use same sac sizes as 
basic models; e.g., 452 uses same sac as 52.
Pen Model(s) Sac Size
5 “Ripple” 15
7 “Ripple” 16
12 PSF, 12V PSF 15
121/2 PSF, 121/2V PSF 13
14 PSF 15
15 PSF 16
16 PSF 18
52, 52V 15
521/2, 521/2V 13
54 15
55 17
56 19
94 16
Patrician (black only, uncommon) 18
Waterman Celluloid Pens
Pen Model(s) Sac Size
3, 3V 16
5 16
7 17
32, 32V 16
52 16
92, 92V 16
94 17
Citation (Taperite or open nib) 16
Commando (ladies’) 14
Commando (men’s) 16
Crusader (Taperite or open nib) 16
Dauntless (Taperite or open nib) 16
Emblem Pen Standard 15
Emblem Pen De Luxe (oversize) 18
Hundred Year Pen Standard 15
Hundred Year Pen De Luxe (oversize) 18
Ink-Vue (Type 1) Ink-Vue (full size)
Ink-Vue (Type 2) (See Richard's repair article)
Lady Patricia Ink-Vue Ink-Vue (Lady Pat)
Lady Patricia lever filler 14
Medalist (Taperite or open nib) 16
Patrician 18
Stalwart 16
Stateleigh (Taperite or open nib) 16


This chart and the information within are © Used with permission.


  1. A correct Pli-Glass sac is not available for the Demi. A Nº 14 vinyl (often sold as “silicone”) will fit when cut to 2" long; there are also some vinyl sacs available that resemble the original “51” sac but are too small for a full-size “51” — these sacs will work well in a Demi.
  2. The correct size sac for the Touchdown TM, as noted in the table, is 15×21/8 Necked. At the time of this writing, this sac was not available from any known source. Substitute a Nº 15 straight sac cut to a length of 23/8".

The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information.