Stainless steel. 1/8" Female BSP x 8.65 mm Female with 0.75 mm thread pitch. The 1/8" side fits great on BSP thread wands, such as the Appia, Musica, Oscar and La Marzocco wands, but not on M10 metric threaded wands. The other end only accepts the "" style Aurelia tip. An (or two if your tip or wand doesn't already have one) is required.