ARESTEKİ TH ÖLÇÜSÜ
Th = Thou = mil = 0.001 Inch = 1 mili inch 

http://en.wikipedia.org/wiki/Thou_(unit_of_length) 
http://www.convertworld.com/tr/uzunluk/Mil.html 
http://www.simetric.co.uk/si_tz.htm 

EK : 1 Inch = 2.54 cm = 25.4 mm