These are Piping Tips which manufactured in England by PME. They are all stainless steel but more importantly ... they do not have seams.
Most other tips (US etc) have a seam even though you may not be able to see it. This is really important where small round tips are concerned. When you start to squeeze your bag and the icing curves as it is coming out of the tip, it is curving toward the seam. When doing small intricate work, this can be a problem.