First set includes long arm hex keys in sizes: .050', 1/16', 5/64', 3/32', 7/64', 1/8', 9/64', 5/32', 3/16', 7/32', 1/4', 5/16', and 3/8'. Second set includes short arm metric hex keys in sizes: 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 8mm, and 10mm. Keys are made of 8650 chrome nickel alloy steel for maximum performance. Keys come in plastic holders that firmly retain the keys in sized marked holes.