Requires air compressor.

The Custom Machined Heads are sizes are for 1/8″ (A4) and 5/32″ (A5) rivets.  You will ABSOLUTELY need this if you are going to build a Zenith kit aircraft.  I personally find it useful to own two of these guns.  I painted one black (for the A4 sized rivets), and one copper (for the A4 sized rivets).  I just leave the respective machined heads installed in the applicable gun and it saves a bit of time and a lot of mistakes.

You do not need to buy this riveter if you have already selected the Complete Tool Kit (unless you think you would like a second riveter).