Porthole in sliding door

If I was to put one of these portholes into my sliding door, anybody know what thickness I would need? I'm presuming the smaller 23/25 mm but I know these things can be deceiving

http://www.ebay.co.uk/itm/220mm-Polycarbonate-Double-Porthole-Window-23-25mm-thickness-caravan-teardrop/322381825162?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D40802%26meid%3D70cc32e57ede42039894e690c0f55baa%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D322372017879

Isn't the sliding door just a single skin I.e 2-3mm?

Raggy wrote:Isn't the sliding door just a single skin I.e 2-3mm?

I don't know! The middle bit is certainly thinner that the edges, but couldn't work out if it was two layers and whether there was any gap between them

Maybe I should just buy the window and cut a circle of ply for inside if it needs to be made thicker to fit it

Raggy wrote:Isn't the sliding door just a single skin I.e 2-3mm?

Yep, single skin.

Ok, I th Nk I'll still buy it, I'm sure adding some ply will do the job, itle certainly reduce the cost of going through the toll going to Wales

elfin girl wrote:Ok, itle certainly reduce the cost of going through the toll going to Wales

They CHARGE you for going to Wales? I'd have thought that you paid to leave....

I wouldn't have thought that would do at all since it is supposed to be for a panel of nearly 1 inch thick which a Hijet door isn't. Would take quite a bit of plywood to bulk it out.

bushwhacker wrote:I wouldn't have thought that would do at all since it is supposed to be for a panel of nearly 1 inch thick which a Hijet door isn't. Would take quite a bit of plywood to bulk it out.

I was thinking of getting some thinner ply and panelling the whole top section so I could put some insulation In between, seeing as that's the side I sleep on and the metal work can be a bit cold on my butt when I turn over in my sleep