This is a triple glazed Mardome roof window. It comes with a 150mm insulated pvc upstand. The opening I had was 90cm cutout in roof. The upstand sides slope inwards and the dome sits on top which is 70cm. If opening space is tight you can put your own upstand 6 x 2 timber to suit a 70cm opening in roof. 

The dome is in very good condition, clear for maximum daylight. When fitted it's like having a light on without using electricity.. super bright. The items are fairly light so posting isn't a problem. The upstand is secured onto the roof with wood screws and exterior silicon . The Mardome is secured to the upstand with 65mm wood screws which I will supply, 12 screws in all. There is a bag of screw caps 12 large and 11 small. I'm  sure I can find the missing one before posting. A  couple of the dome caps have chips. You can buy them but I'd just use a little silicon adhesive to tidy up. A tiny blob of bathroom silicon over the screw heads  before fitting the dome screw caps will do very well. The window is very easy to fit, once you have the square hole opening in the roof. It seals very easily and fits in less than 30 minutes. I'll include a special tube of black flexible roof silicon for sealing the upstand to a felt roof.