They were about £13 each. Goes on front of the frame in the interior mounted with velcro straps and has a zip in the middle to unzip and open/close the window. Keeps the flies and moths out thankfully.
Although Ironically, I found a small spider camped on my net catching the bugs who get stuck on it! Lazy bug-ger can’t build his own web! But I left him be.
It’s an absolute lifesaver- beforehand I’d hate opening the window due to the insects. My bedroom would get extremely warm. Now I can vent air out and not worry about critters.
Olive netting and either duct tape or staples.
Depending on how much you care about your frames
PVC frames, so tape is probably better. Any residue can always be removed with some solvents. But some sealable opening is necessary to open/close the window through it. Sticky back velcro seems like the obvious option to put on the frame. At least a section near the window handle.
The zip is the opening that’s sealable