Acetyl is the modern material for making pipes. While the traditional material for making bagpipes is African Blackwood; it is becoming more difficult to source and therefore ever more expensive, because it needs to be seasoned, ideally for more than 50 years before being turned. Even after seasoning, African Blackwood is prone to shrink, warp and crack over the years.
Acetyl is a material that will not shrink, warp or crack, even in hot climates and is the ideal replacement for blackwood.
Not only do I recommend acetyl pipes from McCallum to my pupils and fellow pipers, I play a set myself. They are easy to set up, and, with the right reeds, sound really great. In addition, I use the V3 Drier System (by Robert Mathieson) and the MacMillan water trap - which mean no moisture gets to the drone reeds.