12.5g Cage Spring Unit 6g Rod Edge Micro Quilted From Shire Beds comes the Metal Master. A 12.5 gauge cage sprung mattress with a 6 gauge rod edge to give outstanding support. This mattress has been specially designed by Shire Beds to suit metal bed frames (hence the name metal master). All micro quilted in a luxury damask containing generous layers of sumptuous fibre fillings.