Polycarbonate glazing is a virtually unbreakable material which is perfect for a cold frame. No more need to worry about any wildlife breaking through the glass, or a falling apple smashing it. All sorts of things can happen in the garden, but with polycarbonate you are getting a very strong and durable material. This also leads into the fact that it is a very safe material. Unlike glass, there will be no dangerous shards that can cause accidents.