The netting itself is slightly stretchy and fixes at 8 points on the tent poles - 4 on the vertical poles corners and 4 more in the middle of the Space Saver bars that now come as standard on most Dark Room and Dark Street tents. If your tent does not have Space Saver bars then they still work, but will not offer quite the same level of support.
They're made of a material that is easy to clean and can be refused many times, although should be discarded in case of spider mite. The net is slightly elasticated to make it a bit more flexible in the event of uneven plat growth.
These nets are absolutely great when used with Space Saver bars - once you start using them you will wonder how you ever did without!
A highly recommended accessory.