Double Screw 'Medium' Bio-Threads® 27G 38mm/100mm (Box of 100)Double Screw Bio Threads are composed of a double Polydioxanone (PDO) filament, wrapped around the needle. This leads to four times the amount of PDO as a regular Mono Thread, leading to a far greater amount of collagen production in areas with deeper lines and poor skin texture. Gauge: 27G Needle Length: 38mm Thread Length: 100mm 100 Threads per box ALWAYS READ THE INSTRUCTIONS FOR USE. ALWAYS FOLLOW THE INSTRUCTIONS FOR USE.