The Rowvane 14PCS Bolt & Nut Extractor Socket Set is thirteen Cr-Mo sockets plus a drive adapter, for bolt and nut heads that are rounded off, chewed up, or painted and rusted past the point a normal socket can hold.
Each socket has a tapered spiral flute machined inside it. You pick the socket one size below the damaged head, tap it on with a hammer until it seats, and turn counter-clockwise with a 3/8" drive. The flutes cut into whatever corners are left, and the harder the fastener resists, the deeper they wedge in — until it backs out with the socket.
No drilling, no cutting, no welding a nut on top. The fastener comes out whole and the part around it is untouched.
Sizes: 1/4" (6.35mm), 5/16" (8mm), 3/8" (9.5mm), 10mm, 7/16" (11mm), 12mm, 1/2" (12.7mm), 13mm, 9/16" (14mm), 5/8" (16mm), 17mm, 11/16" (17.5mm), 3/4" (19mm)
Drive: 3/8" square, plus a 1/4" hex to 3/8" square adapter
Material: Cr-Mo (chrome-molybdenum), marked on each socket body