With help from graphics via the North Sails website, a quick explanation of spinnaker designations. Asymmetrical are shown.

They are categorized by reaching or running and by wind speed. TWA = True Wind Angle; AWA = Apparent Wind Angle; TWS = True Wind Speed;

 

 

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A1

VMG Light Runner (Reduced Size)
Usually for use in less than 10-12 knots TWS
Typical Midgirth 85-95% of Foot
AWA 65-95

 

 

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A2

Medium Runner (Maximum Size)
Usually for use in 10-20 TWS
Typical Midgirth 95-105% of Foot
AWA 90-135

 

 

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A3

Masthead Reaching Gennaker
Usually for use up to 20TWS (Dependant on Angle)
Typical Midgirth 75-85% of Foot
AWA 70-110

 

 

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A4

Heavy Runner (Maximum Size)
Usually for use over 18 TWS
Typical Midgirth 100-107% of Foot
AWA 115-160

 

 

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A5/A6

Fractional Reaching Gennaker (A5), Fractional Running Gennaker (A6)
Usually for use over 18TWS (Dependant on Angle)
Typical Midgirth 75-85% of Foot (A5) 85-100% (A6)
AWA 80-120 (A5), 110-160 (A6)