The spring and wire units made up primarily of coils, helical wires and border wires, which is the inside of an innerspring mattress. Some upholstered furniture such as sofas and loveseats can also feature innerspring units.
Innerspring Mattresses – Mattress Firm
What Is An Innerspring Mattress – Sherwood Bedding
Innersprings – L&P Bedding Group
Innerspring Mattress Guide: Everything You Need To Know – SaaTVa
Innerspring, Hybrid, Latex & Memory Foam Mattresses – Sleep City Mattress Center