ZPV Pilot Chamber Finish Reamers are precision-manufactured on Swiss machinery. The use of Austrian HSS S705 Bohler Steel makes these reamers durable and ensures they will hold an edge to cut a precise chamber. The "Freebore" or "throat" is the tapered section of the chamber immediately in front of the cartridge. Reamers that are listed as "without freebore" do not cut that last section of the chamber, so if you use it, you would also need an additional reamer referred to as "with freebore" in order to complete the chamber. Some gunsmiths prefer to cut the throat section separately so they order both a "without freebore" and a "with freebore" reamer. ZPV says this is often preferred for larger-calibers because the reamer can be damaged more easily at those sizes if you use just one reamer for the whole process. Gunsmiths that would like to cut the chamber in one-shot can use a finisher reamer. Also, some gunsmiths prefer to use a "roughing" reamer to start cutting the chamber, then ...