The Master Lock No. 6321 ProSeries® Shrouded Padlock features a 2-1/8in (54mm) heavy steel body that withstands physical attack and a 3/4in (19mm) tall, 5/16in (8mm) diameter hardened boron alloy shackle for superior cut resistance. Ideal for transportation and industrial applications, the iron shroud protects the shackle from bolt cutters and a dual ball locking mechanism resists pulling and prying. The high security, rekeyable 5-pin cylinder with spool pins is virtually impossible to pick.