Gauge HT Grand RegulationNew, our HT Grand Regulation Guides have been designed and made with a higher working temperature of 70C (158F) As like our standard guildes measurements assist with: 6 Blow distance 43mm 48mm, 6 Set off let off 2mm 7mm, 6 Damper lift, 21. 5mm 24mm can also be used to help judge checking, improved 6 Key height 62mm 67mm. More stable than wood in order to stay accurate but still flexible. Made in a bright white to enable easy reading when in action.