tuning core as they does not implement core tuning. cod. SBK-50 useful space for the coil = 5,2 mm , max 10 turns , max wire Ø 0,3 mm, max inductance ~ 500 nH useful space for the coil = 5,7 mm , max 4,5 turns , cod. SBK-51 max wire Ø 0,6 mm, max inductance ~ 100 nH useful space price 0,45 € -- 0,40 €