The sealskins mtb mid hydrostop sock a performance mid weight mid length waterproof sock featuring hydrostop designed specifically for mtb offers a perfect balance of warmth and breathability sealskins mtb mid hydrostop sock featurs mid weight mid length sock offering a perfect balance of warmth and breathability constructed with our proprietary stretchdry waterproof breathable and windproof technology hydrostop silicone free elastic taping provides a barrier to water