Check your current set for the accuracy, my 1.5 are actually 1.54 to 1.56, same on the new set of 1.6, (actually checked at the retainers 1.64 to 1.66) that I bought three years ago I use a ail indicator and set the lash at zereo, measure the actaul lift at the retainers and do the math, lobe lift times the ratio for theoritical lift versus actual lift at the retainers