Originally posted by bendingiscool Is it a duplicate of a previous cylinder, if so that would explain why you can't change its inputs. Chris Hi Chris, Yes it is. It is a duplicate of a cylinder I used earlier for a Boolean operation. I saved it because I wanted to save the outer dimensions so it would fit in a sleeve. I did not realize that duplicating a polygon object would limit its uses later on. I guess I should have used the duplicate for the Difference operation and saved the original. I have not got the input/output thing worked out yet so I will read up on that more today. Thanks a lot for explaining this, Ron