Cheap Springs

Hey guys, just searching the web today for some stiffer springs for my 570 when i ran across some at speedway motors.

AFCO 1-7/8 Inch I.D. Coil-over Springs, 10 Inch – Speedway Motors, America's Oldest Speed Shop

They are 150 lb spring rate and look like the same diameter (maybe)? but they are only 30 bucks…What is the difference between these and the $99 pair at