kích cỡ (Đường Kính): PN20 20mm x 3.4mm ;PN20 25mm x 4.2mm ;PN20 32mm x 5.4mm ;PN20 40mm x 6.7mm ;PN20 50mm x 8.3mm ;PN20 63mm x 10.5mm ;PN20 75mm x 12.5mm ;PN20 90mm x 15mm ;PN20 110mm x 18.3mm