Quick-blow or fast-blow glass fuses are deliberately designed to be weaker, so they immediately fail or blow in order to protect a circuit or device. They are mainly used in calibration or computer equipment. In contrast, antisurge or slow-blow fuses can withstand a high current overload for a short period without failing. Decide whether an antisurge or quick-blow fuse is more appropriate for your use. Quick-blow fuses are denoted by the letter 'F,' so a 2-amp quick-blow fuse would have 'F2A' embossed on it.