No Sag Springs, or, if you're using professional, technical terms, Zig Zag springs, are a long lasting alternative to coil springs. They can be easily replaced and tightened over time, and can create a custom crown shape on the surface of your seat. Using the right tools and fasteners, these can be a more affordable alternative to coil springs, just in saving time and energy on the tying process alone. It's a learning curve to get it right, but a lot of that just comes with practice and experience. Thinner gauges mean more flexibility and less strength. Thicker gauges are typically used for seats and thinner ones for seat backs. The higher the number of Gauge, the thinner the spring metal (12 Gauge thinnest and more flexible, 9 Gauge thickest and stiffer).