Metric 4mm thread with .7 pitch.MED=8PLY ( this can vary lug to lug depending on the length of it's screw inserts - but this is a good guide point to start ),High quality drum lug mounting screws. These screws are NOT included with our lugs, since we offer many lengths for different shell thicknesses. SHOULD work with most shells close to 8ply or 6mm or 1/4in thick.