5.3 Class of extrusion profiles
It is generally said that there are three types (classes) of extrusions.
These are:
  • Class one, these are simple profile, with no hollows.
  • Class two, these are single hollow profiles.
  • Class three, these are multi hollow profiles.

These three classes are also often broken down further. Please click on the links to see these differences.
Section type
E,F,G,
H,J ,
K,L,M,N
5.3.1 Class I
5.3.2 Class II
5.3.3 Class III
5.3.4 A,B,C & D
Category A
Simple bar
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Category B
Shaped bar
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Category C
Standard sections
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Category D
Simple solid sections
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5.3.5 E,F & G
Category E
Semi-hollow sections
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Category F
Sections with thin walls or wide sections
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Category G
Sections with difficult tongues or narrow inlets.
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5.3.6 H & J
Category H
Tubes
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Category J
Simple hollow sections
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5.3.7 K,L,M & N
Category K
Difficult hollow, or more than two hollows.
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Category L
Tube with external ribs
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Category M
Tube with internal ribs
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Category N
Large or wide hollow sections
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