A conversion kit comes with the threaded barrel, a compensator and a metal guide rod with heavy spring. At the time, the kit's ran $330 or so.  I ordered the kit and got another used Glock 21 off GunBroker.  My kit delivered in early 2012 but it was a kit for the compact Glock 30 ... not what I had on hand at the time.  A quick call to the company had the correct kit headed my way with lots of apologies.

By Sept my handgun was together :

For safety reasons, they lengthened the case 1/16th of an inch so that it could not be loaded in .45 ACP chambered handguns (that'd be bad).  They also thickened the base to handle the 40,000 psi working pressures compared to the 19,000 of the ACP.  Starline makes brass.  I fully intended to use a 230 gr .451 xtp and try for that 1300 fps mark but after talking with my brother a little bit, I decided to go a bit heavier.  I bought a box of 250 gr. .452 xtp's and started development.  I ran outa time before winter set in but once I got back to it in the spring of 2013, I settled on a load using 10.2 gr. of Power Pistol achieving almost 1200 fps.  This is a very snappy load in the light Glock, even with the compensator but a fun one to shoot and own.   kor