Made of BUNA-N 70 durometer rubber compound. Creates a tight seal for fluid or gas connections. Handy kit for shop toolroom or toolbox. On hand when needed saves time and money. Plastic compartment box is easy to store. The Precision Brand® 350 Piece Metric O Ring Asst contains: 15 – 2mm x 3mm; 15 – 2mm x 4mm; 15 – 2mm x 5mm; 15 – 2mm x 6mm; 15 – 2mm x 8mm; 15 – 2mm x 10mm; 15 – 2mm x 12mm; 10 – 2mm x 14mm; 10 – 2mm x 20mm; 15 – 2.5mm x 10mm; 15 – 2.5mm x 12mm; 15 – 2.5mm x 14mm; 15 – 2.5mm x 15mm; 15 – 2.5mm x 16mm; 10 – 2.5mm x 17mm; 10 – 2.5mm x 19mm; 15 – 3mm x 19mm; 15 – 3mm x 20mm; 15 – 3mm x 22mm; 15 – 3mm x 24mm; 10 – 3mm x 25mm; 10 – 3mm x 27mm; 10 – 3mm x 28mm; 10 – 3mm x 30mm; 10 – 3mm x 32mm; 5 – 3mm x 33mm; 5 – 3mm x 35mm; 5 – 3mm x 36mm; and 5 – 3mm x 38mm.