CON00898-B-50    3/4" screw Adapter with #4 metric screw threads to twist in to the Concho back, other end is milled like a wood screw for attaching screw back Conchos to any piece of wood furniture, wood frames or any wood craft project, for best application drill a 3/32" pilot hole about 1/4" deep package of 50.

Here's what the description means

M = Metric thread designation

.7 = Pitch (distance from thread to thread), in millimeters