An essential item for dispensing opticians, the ABDO Frame Rule was designed by George Clayton and is produced by the Association of British Dispensing Opticians.
 
The rule will enable the user to accurately measure the following:
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Interpupillary Distance (PD)
Boxed Lens Size (Horizontal and Vertical)
Distance Between Lenses
Boxed Centre Distance
Crest Height
Bridge Projection
Distance Between Rims
Bridge Height
Bridge Width
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The white plastic rule which is 155mm x 60mm, measures 11 different frame dimensions and comes complete with a full instruction manual.