Snap-on Tools USA NEW 81 Piece 1/4 Drive. 6 Point Chrome Flank Drive Xtra Shallow / Semi-Deep / Deep Master Set in Tray. (If interested in another tray color send a message and it can be arranged). YTMM4.5 = 4.5mm. YTMM5.5 = 5.5mm. YTMMS4.5 = 4.5mm. YTMMS5.5 = 5.5mm. YSTMM4.5 = 4.5mm. YSTMM5.5 = 5.5mm.