The P-70Ex 70mm Extension Ring from AquaTech increases the length of compatible P-series lens ports by 70mm to allow them to accommodate longer lenses. The ring screws directly onto the housing and the port screws into the ring.
For Use on the Following Lens Ports:
P-65 flat port with Nikon 17-55mm f/2.8 lens
PD-65 or PD-85 dome port with Schneider 28mm f/4.5 LS