You've lost me again. I screw the sturdy holder over the threaded end of my FlexPen. I pull the sturdy holder away from the FlexPen, leaving a less sturdy plastic part holding the needle. I inject, then use the sturdy holder, by pushing it over the needle, to grip the less sturdy plastic part and unscrew it. The needle and less sturdy part are now inside the sturdy holder, and all together they end up in my sharps bin.
Perhaps you could find a picture of yours ?
Geoff
p.s. my picture may not be of Gluco Rx but it does look like my Gluco Rx. Two sturdy holders with their less sturdy plastic part (with it's needle) and a less sturdy part on its own.