10MHz, 18pf, Citizen HC49US Low Profile Oscillator Crystal. The HC49US package size fits all mikroElektronika development boards.
A 10 MHz crystal is a perfect fit for the PIC16 and PIC18 microcontrollers. This crystal is the correct value to create 40MHz for PIC18 by using the internal x4 PLL frequency multiplier. This can reduce external high frequency noise and enables very fast operating speeds.