These are "Shining Adjuster Screws" with crystals decorating the top of L-shaped adjuster screws. The crystals are crystal aurora, which is representative of the sparkle that rhinestones are known for. They shine with an iridescent glow. If you're unsure which color to choose, this is the one. Preciosa is a Czech crystal brand, second only to Swarovski. The beautiful cuts, transparent glass, and stunning effects are truly impressive. ・Crystal Aurora, Transparent AB Coating AB coating was jointly developed in 1955 by Swarovski and Christian Dior. It is an abbreviation for "aurora borealis," the Northern Lights, and is a beautiful effect (coating) that changes color depending on the viewing angle. The screws are compatible with L-shaped adjusters for violins and violas (Wittner, Stradpet, etc.). Screw diameter: JIS M2 Made of steel (black), with a pointed tip. Crystal: Preciosa flatback ss20 This product includes only one screw. Adjusters, tailpieces, and instruments are not included. When replacing the screws, it is recommended to protect the instrument with a cloth or similar material to prevent scratches.