If you are looking for a large capacitance (above 500 mfd) or a high voltage (up to 500 Volts) capacitor then you are probably looking for a large can electrolytic capacitor, commonly referred to as a computer grade capacitor.
If the part you are replacing begins with one of the following series, you are looking for a large can electrolytic capacitor, usually identified by having two screw terminals (a high post has an insulator off the top of the can).
Typically large can computer grade capacitors will have a capacitance measured in microfarads (mfd) or the designation uF. This capacitance is represented in numbers (example 10,000 mfd or 25,000 uF). Next you will see a voltage on the unit, designated by a V or WVDC (working voltage). 99% of the time, these capacitors are measured in DC (direct current) voltages. This is the constant voltage these capacitors will withstand.
Important in replacing these capacitors is not only the capacitance and voltage but also the size of the unit. The diameter of these capacitors comes primarily in the following diameters (in inches):
In most cases these large can electrolytic capacitors are mounted to either board or chasis with round clamp VR series.
95% of the cans will fall into these categories. The height of the units can vary from 2.125 to 8.75 inches.
An important piece of information about large can electrolytics is their tolerances. Typically voltages from 6 volts to 150 volts have a tolerance of -10% +75%. This is important because a capacitor of 10,000 mfd at 50 volts can, in actuality, read on the positive side up to 17,500 mfd and be within tolerance. So when choosing a replacement capacitor, typically you have the flexibility to choose a mathematically suitable replacement. Above 150 volts up to 450 volts the typical tolerance is -10% +50% again, giving you flexibility when choosing a computer grade capacitor replacement.
These capacitors typically come with a PVC insulating sleeve.