Typically, A4 grade stainless steel costs slightly more than A2 because of its enhanced chemical and production properties. The extra cost can be justified, however, because hardware made of A4 stainless steel is extra resistant to tarnish and corrosion, enabling it to last a very long time. Where the L1 dimension is blank the screw is fully threaded. The L1 dimension is for reference to the DIN document only. A4 stainless is often used in marine or chemical environments as it has greater corrosion resistance than A2. The most common thread type in production today. Usually specified as M then a number x another number. This signifies the thread diameter and the length of the fastener. We wish all our customers a happy but safe Christmas and New Year and let's all hope for saner and quietly normal year for 2023!