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Cap Sizes and Neck Finishes

Plastic Closures

There are two basic types of plastic closures used for scientific applications: thermoset and thermoplastic.

Thermoset closures cannot be remelted after they are formed. They provide the widest range of chemical compatibility and they exhibit the most tolerance to temperature of all plastic closures. Because thermoset closures are rigid, they provide the most consistent adherence to close dimensional tolerances. Common resins include urea, phenolic, and melamine.

Thermoplastic closures can be remelted after they are formed. They are known for good impact strength, cost effectiveness, and pliability. Common resins include polypropylene (autoclavable) and polyethylene.

 

Metal Closures

Metal closures offer the widest range of temperature tolerances and are very resistant to fracture from impact. A metal closure is manufactured from either steel (coated with anti-corrosive coating of either chromeplate or tinplate) or aluminum.


 
Closure Size Info
 
Screw thread closure sizes are expressed in two numbers.

The first number refers to the closure diameter (in mm) and the second number represents the GPI finish (the top of the container).
 
For example, a neck size of 28-430 has a diameter of 28 mm and fits a container with a 430 GPI thread finish.  
 

 

Common Cap Finishes



 

 

     
Selected Heights of Standard Closures
 Closure Size
(mm)
400 Finish
410 Finish
415 Finish
425 Finish
8
-
-
-
.262-.280 in
10
-
-
-
.273-.291 in
13
-
-
.428-.458 in
.298-.316 in
15
-
-
.533-.563 in
.298-.316 in
18
.359-.377 in
.499-.529 in
.593-.623 in
-
20
.359-.377 in
.530-.560 in
.718-.748 in
-
22
.359-.377 in
-
.813-.843 in
-
24
.388-.406 in
.622-.652 in
.933-.963 in
-
28
.388-.406 in
.684-.714 in
1.058-1.088 in
-
33
.388-.406 in
-
.245-1.275 in
-
38
.388-.406 in
-
-
-
43
.388-.406 in
-
-
-
45
.388-.406 in
-
-
-
48
.388-.406 in
-
-
-
53
.388-.406 in
-
-
-
58
.388-.406 in
-
-
-
63
.388-.406 in
-
-
-
70
.388-.406 in
-
-
-
77
.467-.485 in
-
-
-
83
.467-.485 in
-
-
-
89
.515-.533 in
-
-
-
100
.577-.595 in
-
-
-
110
.577-.595 in
-
-
-
120
.665-.683
-
-
-