The Heavy-duty first-stage holder has two different sides one is an LP with 3/8 UNF threads and the other one is an HP with 7/16 UNF threads.
The best way to use this tool is by clamping it in your vise so you have your hands free to work on your equipment.
 
The first stage holder - heavy-duty version is precision machined from stainless steel.
 
GTIN: 8720828266601