Stainless steel round beads used as spacer for other beads with a diameter of 3 mm and with a hole for a thread with a diameter of 1.8 mm. The beads are not hollow and the edges of the hole for the thread are finely ground. The beads are made of stainless steel type 304.
The stainless steel (surgical) alloy from which the beads are made is referred to as SAE 304 (also known as A2 stainless steel, or 18/8 stainless steel). In addition to iron, as the main component, it usually contains around 18 % chromium and 8 % nickel. Detailed information on the composition and properties can be found at English wikipedia.
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