Offset (Karr) Coils [caption id="attachment_705" align="aligncenter" width="642"] Offset Coil System Image from Bedrooms & More, Seattle, Washington[/caption] Offset coils, also called Karr coils, were invented in the early 1900s by Frank Karr, who also started the Spring Air mattress company. They were developed from Bonnell coils, the original support for innerspring mattresses. Since the inception of offset coils, they have been used by many other mattress companies. The...