When it comes to slide playing, and in this section we are still talking about acoustic, there are 2 instruments that Al uses. An Amistar Style O from 2007, handbuilt by Amistar in Prague (they all are handbuilt), and a National Delphi from 1998. The Amistar is always used in G tuning, and the National Delphi is for D tuning. Look at the photos next to this section.