Needing to replace the handle on your 3M Scotch-Weld PG II pneumatic glue gun is rare. However, it does happen on occasion from general wear and tear.  We recommend that if you have 16-20 PG II glue guns in operation that you have one 3M part 9221 on hand to avoid down time.  For detailed instructions on replacing the handle check out the 3M PG II Glue Gun Owner's Manual.