Twin-Wall Polycarbonate hollow Sheet for 18mm: Size 1)thickness: 1.5mm--15mm 2)Length: no limit ... :2100mm UVA&UVB protect Twin-Wall Polycarbonate hollow Sheet for 18mm Features: 1) Light transmission: up to 88% 2) Impact resistance ... 4mm,5mm,6mm,7.5mm,8mm,10mm,12mm,14mm,16mm ,18mm. 4) Color: clear, lake blue, green, blue, opal, bronze, gray ...