After doing a lot of reading this weekend I found out that there is no standard for measureing the stud length,, woodys measures from the top of the backer plate to the tip of the stud, while others measure from the top of the track to the top of the lug then add on to that measurement, but there is one measurement they all use, the over all length from the top of the head to the tip of the stud,in my case the measurement of the track thickness plus the lug is 1.500 inches so if I wanted 1/4 inch penetration I would need a stud that has a 1.750 over all length,now useing woodys way of measureing from the top of the backer to the tip the 1.375 would yeald the same 1/4 inch penetration. the numbers are confusing it just depends on which brand one uses.