These standard inserts are collarless and can be set flush with or sunk below the wood surface. Made from steel and zinc plated, they have an unthreaded lead to support easy assembly. They are available with M6, M8, 1/4-20, 5/16-18 or 3/8-16 internal threads, with a broader range of lengths than the SK30 or SKD30 inserts. All are driven with hex bits. Made in Germany.