Grubs Mens Highline Boots Sage Green. Stay warm and dry when exploring the countryside with the Highline Boots From Grubs. Offering a traditionally styled full rubber wellington boot, the Highline Welly Boot offers a adjustable calf for a flexible fit. With Trakâ ¢ sole and a 6mm Nitrocellâ ¢ footbed for a cushioning and insulated feel for all day comfort whilst the sole provides a deep tractor like tread for powerful traction whilst on soft ground. With Hexzorbâ ¢ technology insert in the heel to provide shock absorbing qualities whilst reducing impact pressure on hard surfaces, the the Highline Welly Boots are complete with a Super-Driâ ¢ lining which offers a moisture wicking liner whilst the insu-foam ultraâ ¢ provides ultimate comfort without heat or sweat building up. The Highline Boots have a comfort range of -10 ºC to +20 ºC.