Aluminum extrusion "series" define the base dimensions and measurement systems of modular T-slot framing. The 10 Series and 15 Series are fractional (inch) systems, while the 40 Series is a metric system based on millimeters. 

 

Fractional Series (Imperial)

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These series are common in North America and use base dimensions in inches. 

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• 10 Series: Based on a 1-inch profile unit. A standard 1010 profile measures 1" x 1". The T-slots typically have a 0.255" to 0.26" width. It is considered a lighter-duty series suitable for smaller frames and enclosures.

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• 15 Series: Based on a 1.5-inch profile unit. A standard 1515 profile measures 1.5" x 1.5". These have wider T-slots, usually 0.32" to 0.322". This series is more robust and designed for heavy-duty industrial applications. 

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Metric Series

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The metric series is a global standard and uses profiles measured in millimeters. 

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• 40 Series: Based on a 40mm profile unit. A standard 4040 profile is 40mm x 40mm. T-slots in this series typically measure 8mm or 10mm wide. It is equivalent in strength to many heavy-duty fractional profiles and is a standard for industrial automation and machine bases.