I. Quartz crystal unit also called quartz crystal, and the types are: 1.HC-49/U 2.HC-49/S; HC-49/S-SMD 4.HC-50/U 5.SMD-5*7 6.206 308 309 3010 column quartz crystal unit clock crystal 　　II. Crystal Oscillator also called clock oscillator and the types are: 1.SMD-5*7;2.Half size square, DIP-8 3. Full size rectangle, DIP-14