The springs have different stiffnesses and are large enough (14-21 cm) to be used in our physics experiments in the spring force and elastic energy to be used.
Pros
Compressed Spring Dimensions: 6.25" x 0.5", 8" x 0.6", 6.5" x 0.75", 7.5" x 0, 6", 8.25 x 1", 9" x 0.4"