I'm thinking this problem is unique to v22, because I did not have this problem before upgrading to v22 a couple of days ago. Basically, the problem is just what the title of the thread says...I try to insert a part into an assembly and a different part, the wrong part, gets inserted! Yeah, can't happen, can it? I've attached component and assembly files so you can see for yourself. A little background first...the sheet metal assembly consists of 5 parts. At one point in the design, the side pieces were both the same part number (-008). But, the side pieces needed different holes in them, so I created -009 from -008. Identical except for the holes. Now, when I try to replace a Side Panel -008 with -009, -008 comes back. If I delete one of the Side Panels, go to Insert Design, select the -009 part, -008 gets inserted! If I start over and create a BRAND NEW assembly, 008 gets inserted when I've actually selected -009! Other things I've tried (to no avail) : Copied the files to a new folder Renamed ALL the parts Renamed the assembly Shut down the computer completely and rebooted None of the above action have helped. I guess the next obvious step is to just redraw -009 from scratch to remove any association with -008. Right? Any other suggestions? Neal Cooper PS : v22 looks like a great upgrade. I've watched most of the videos describing the new features. Looking forward to using the new stuff.