These are the measurements given most commonly when ordering a picture frame. ( At LeCira all sizes are quoted giving these size references ). Often referred to as the "glass size" it is the size of the piece of glass required that will not fall through the central aperture in the frame.

The general reason for requiring these sizes is to either match as close as possible an existing design or the check whether the artwork you wish to have framed will fit into the rebate of the chosen design. As some mount combinations can often be more than 10 mm in depth. Example, Plain glass 2 mm, double mount 3 mm, artwork on foamcore™ 5 mm and then a backing board another 2 mm, total 12 mm Making it difficult but not impossible to fit into a 10 mm rebate, a cost would therefore be incurred to work around the problem.

Aluminium mouldings are measured slightly differently than wood, first they have a set rebate that cannot be extended and the width visible is nearly always smaller than the actual width of the design. Care should be taken when measuring an existing frame as the frame size is measured from the inner wall of the back edge.