Thomastik Jazz flatwound JF344 43-100 bass strings set for 4-strings fretless electric bass. Nobody knows flatwound bass strings better than Thomastik-Infeld. Spirocore strings by Thomastik-Infeld have been legendary among upright bassists for decades. Now the electric bassist can also experience the Thomastik-Infeld sound. Thomastik-Infeld utilizes a highly pliable steel core which is wrapped with a silk inlay. The outer winding is a true ribbon flatwound constructed of a special nickel alloy. The result is an incredible depth of tone and an enhanced fundamental which is unavailable from any other flatwound.