Blue Label is the top grade of cedar shingle or shake. The other grades are Red and Black label; these are not recommended for roofing in the UK.
Blue Label Shingles are 100% clear, 100% edge grain and 100% heartwood. The Western Red Cedar Shingle and Shake Bureau is a member organisation that is recognised as having some of the highest quality standards. It owns the trademarks of CertiGrade and CertiSplit. Care must be taken when buying shingles and shakes as the quality can be very variable. Poor quality shingles can exhibit cell collapse, contain too many narrow shingles or not have sufficient coverage.
Marley Eternit takes great care in assessing the third party accreditation of its suppliers and only uses Canadian Shingles and Shakes.