Haskins and Starfleet pattern blue spring to suit Haskins and Starfleet garage doors from 10ft to 14ft wide. Available in three size options, the spring you need can be identified by its colour and its number of coils, length over coils and overal dimensions:
 
Grey spring
Number of coils: 93.
Length over coils: 18 1/2" (470mm).
Overal length including hook: 21 1/2" (550mm).
Diameter: 1 5/8" (41mm).
 
White spring
Number of coils: 89.
Length over coils: 18 7/8" (480mm).
Overal length including hook: 21 1/4" (540mm).
Diameter: 1 5/8" (41mm).
 
Blue spring
Number of coils: 71.
Length over coils: 18 1/4" (464mm).
Overal length including hook: 21 1/4" (540mm).
Diameter: 2 1/8" (54mm).