Double Coned Coil Upholstery Springs
These springs are used for traditional upholstery.
They are coiled and have a large tied off coil on both the top and bottom making it easier to fix to the furniture.
The spring wire is measured by gauges. The higher the gauge the softer the spring. Hard springs are used for seats and soft springs are used on the back.
The length of the spring is measured between the two knots on the spring.