＜br>Made from 18-8 stainless steel, these screws have good chemical resistance and may be mildly magnetic. Length is measured from under the head. ＜br> Metric screws are also known as A2 stainless steel screws. ＜br>Coarse threads are the industry standard; choose these screws if you don't know the pitch or threads per inch. Fine threads are closely spaced to prevent loosening from vibration. ＜br>They are not compatible with coarse threads. Screws that meet ISO 21269, and ISO 4762 (formerly DIN 912) comply with standards for dimensions.