By default, all JANSSENS's greenhouses are made for 4 mm tempered glass. It is maintenance-free and long lasting. If it is possible, glass is delivered as single panel, not as small overlapping panels. It is 6 times stronger than normal and more resistant to wear and tear. So it minimizes the risk of damaging. In addition, if glass breaks, then it breaks into thousands of fragments, so the risk of injury is very low. All edges are polished to ensure ease of assembly and to avoid cuts. Quality and safety first!