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.