The flutes are made in my workshop from solid delrin rodstock. This is an acetal polymer valued in engineering for it's rigidity and toughness and its resistance to impacts. It is possible to make an excellent flute from delrin.
The material has become popular in the last decade or so for these flutes as it is very dense and is capable of taking a fine edge which is a very important property for the blowing edge of the embouchure hole on a flute. An overly rounded blowing edge on an embouchure hole makes a flute difficult to play and is a common problem on antique wooden flutes which have seen a lot of use.
The flutes are given a matte finish which helps to give the surface more grip for the player.
The metal tuning slides which consist of two tubes, one of which slides inside the other, are made from copper or brass and the exterior of the outer slide tube is given a heavy nickel plate.
The metal rings on the body of the flute are brass but are also given a heavy nickel plate. The flutes which don't have metal rings generally have integral delrin rings turned into the body.
Flute headjoints traditionally have a cork stopper in the bore a short distance above the embouchure hole, which serves as a reflector for the sound waves. Cork works well for this but makers are experimenting with other materials for the reflector, including delrin. A delrin stopper has a smooth, hard facing which can act as a more efficient reflector and in any case is more durable than cork. My flutes with metal tuning slides have a white delrin stopper with a rubber O-ring for sealing the bore of the headjoint. The endcap at the top of the head also has a rubber O-ring.
My flute models which don't have metal tuning slides have the traditional cork stopper as reflector.