Green air conditioning rubber O-rings. Material - HNBR. Hydrogenated Nitrile Butadiene Rubber. Contains - 20 pieces of each - 3mm x 1mm, 4mm x 1mm, 4.5mm x 2mm, 5mm x 2mm, 6mm x 2mm, 6mm x 2.5mm, 6mm x 3mm, 7mm x 2mm, 8mm x 2mm. Contains - 5 pieces of each size - 9mm x 2mm, 10mm x 2mm, 12mm x 3mm, 13mm x 3mm, 14mm x 2.5mm, 17mm x 2.5mm, 18mm x 4mm, 20mm x 2mm & 22mm x 2mm.