Long nose makes everything easier as the nose slides into the vitreous and provides telescopic adjustment whilst fitting. I HIGHLY RECOMMEND THIS PART.
The top of the adaptor connects to your flue liner (self tapping screws to secure). The bottom of the adaptor connects to your vitreous flue pipe (pipe that leaves your stove) using two metal to metal self tapping screws. You will actually need to drill a small pilot hole for the self tappers (due to the stainless being extremely tough).
Very impressed with the level of detail on the stovefittersmanual.co.uk. After reading a lot of the info I felt like I could actually install my own stove saving a couple of thousand - and it did its in and working. One of the things recommended was this long nose adapter. Im glad I bought it because it made final connection a lot easier due it protruding down from the fireplace ceiling plenty to align with the black pipe from the stove itself. Because its long it gives real confidence that its mated properly to the adapter and enables you to manoeuvre the black pipe + adapter into final position without feeling like you might be bending something. Highly recommended. One tip though - drill through self tapper pilot holes before fitting to flue liner so they are straight otherwise its quite difficult to line up the screws (which go in straight) with inner pilot hole if you drilled it at a slight angle.
Connecting the stove had to be done with the liner in place - having measured everything then cut the liner the adaptor provided just the movement needed to get all the joints properly together. Bolts would have been nice but no problems with pre-drilled holes and self-tappers.