Three mini-size mercerized cotton lase strands twisted together.

yarn-paradise.com website says:

“Weight : 50 gr. each skein. 400 gr. Each package
Length : 125 m. each skein. 1000 m. Each package
Fiber Content : 100% Mercerized Cotton
Needle Size : 4 mm / US 6
Yarn Thickness : 2 Fine: Sport, Baby
Washing Instructions : Hand Wash at 30ºC / 86ºF, lay flat to dry.