This part of ISO 10424 specifies requirements for the following drill stem elements: upper and lower kelly valves; square and hexagonal kellys; drill stem subs; standard steel and non-magnetic drill collars; drilling and coring bits. This part of 10424 is not applicable to drill pipe and tool joints, rotary shouldered connection designs, thread gauging practice, or grand master, reference master and working gauges. A typical drill stem assembly to which this part of 10424 is applicable is shown in Figure 1.