Correx is a lower quality twin wall polycarbonate sheet, which is good for
making shelters, frames. cloches etc, whilst "Twin walled Poly carb" is
usually used to describe the higher quality product as against "Triple
walled"
Could be worth contacting
http://www.kaysersberg-plastics.com/index.htm ( Products..construction)

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David Hill
Abacus nurseries
www.abacus-nurseries.co.uk