Our Review – Helinox Ground Sheet Chair One: The perfect accessory for uneven or soft ground. The Helinox Ground Sheet for the Chair One snaps into each of the four legs of your chair and levels the load to prevent your chair legs from sinking into the ground. Specifications - Helinox Ground Sheet Chair One: Designed to work with the Chair One Chair footprint for use on sand or muddy ground Chair legs slide into corner pockets Centre attachment secures to chair frame Folds for easy storage Size - 14.5" x 12.5" Helinox Ground Sheet Chair One / Black