A snake like spring usually stretched from front to back of seat and fixed to the seat frame with clips (found here).
Seat springs are made of the thicker 9 gauge wire we offer these in 16 different lengths from16 inches up to 32 inches in long.
The 11 gauge wire is suitable for chair backs and is sold by the foot. It will be cut to your required length and sent to you in a coil form but will straighten easily for you to fit. Use the same clips as the seat springs to fit to the frame.
TOP TIP: To stop springs from spreading apart make sure they are placed no more than 2-3 inches apart and/or use silent wire fixed with clips about 6 inches from the front of the seat. View silent wire and clips
TRADE TIP: The most robust cover to use over the springs is insulator padding . This should be used with the hard side against the springs and can be fixed but is best left oversized on two edges allowing the springs to flex.