Firetrap 3 Pack Invisible Socks Men's. These Men's Firetrap 3 Pack Invisible Socks have been developed with soft feel fabric with an element of elastane for great comfort with the right of amount of stretch whilst the low-cut design means that the socks won't be seen. Men's Invisible Socks- Low-cut design - Soft feel- 75% Acrylic 22% Nylon 3% Elastane- Machine washable. Colour: black