The critical specifications of a capacitor are the dielectric constant, dissipation factor, dielectric withstanding voltage, and insulation resistance. Dielectric constant depends on the ceramic material used. The table shows different dielectrics and some of their specifications. As you can see NP0 has the lowest dielectric constant, followed by X7R which has a significantly higher constant, and Y5V which is higher still. This is why the capacitance values for X7R capacitors are much higher than NP0 capacitors, and Y5V has higher capacitance than X7R. The capacitance change vs temperature is very small for NP0 parts from -55°C to 125°C, and gets larger for X7R, then even larger for Y5V. So, the more capacitance a material provides, the lower the stability of capacitance over temperature. Dissipation Factor is the percentage of energy wasted as heat in the capacitor. As you can see, NP0 material is very efficient, followed by X7R, then Y5V which is the least efficient of the three materials. Dielectric withstanding voltage refers to the momentary over voltage the capacitor is capable of withstanding with no damage. Insulation resistance is the DC resistance of the capacitor, it is closely related to the leakage current.