Alfa Tools solid screw inserts - carbon steel. Alfa lock inserts will not back out or vibrate loose. Immediately on installation, micro-encapsulated adhesive begins to set, and the newly installed inserts can be fastened within minutes the adhesive continues to set overnight until completely set. The adhesive seals against all liquids and gases to a pressure of 6,000 PSI when fully cured and bonds to virtually all metals. Use a standard screw and bolt extractor to back out a damaged insert and then replace it with a new insert.