100% Polyester Sewing Machine Threads 400 Spools * Packed in 4 boxes of 100 spools each. 90 Different Colors in Each box. * 100% Color Fast. will NOT Bleed or Run in Hot or Cold Water. * Very High Tensile Strength, for high speed stitching * Can be used for Hand Sewing / Machine Stitching / Serger / Light Quilting