Good quality copper
"Does exactly what it should in my reflux column. The copper packs evenly, gives plenty of surface area and the vapour runs clean through it. Quality: Solid pure copper, not flimsy. It holds its shape, doesn’t crumble or shed, and cleaned up easily before use. Selection: Good to find a proper copper packing option in a handy size at a fair price, and delivery was quick. Happy with it and will order again."