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 guages mean more flexibility and less strength. Thicker guages are typically used for seats and thinner ones for seat backs. The higher the number of guage, the thinner the spring metal (12 guage thinnest and more flexible, 9 guage thickest and stiffer).