Hollow extruded shapes are classified as follows:
A hollow extruded shape having a single void with no internal or external protrusions, and which is greater than 15 mm in diameter or 177 mm≤ in area. The void may be round, square or rectangular, provided that the width/depth ratio is less than 5:1. It has uniform wall thickness except that a non- uniform wall is allowed at corners having internal or external radii up to 7.5 mm.
A single void hollow extruded shape other than a Class A shape, or a solid shape incorporating a single semi-hollow area classified as a hollow.
A hollow extruded shape having two or more fully enclosed voids.
Any hollow shape that incorporates a semi-hollow area, or any solid shape that incorporates multiple semi-hollow areas that are classified as hollows.
Yacht Mast Extrusion
A hollow or solid extruded shape, which is basically round or elliptical in section and which incorporates a sail track or has provision for a sail track, used in the manufacture of masts and booms for yachts.