This here is a 10 pack of the classic 1N4001 power blocking diode. These are good for reverse polarity protection (put it between your DC power jack and circuitry to avoid a negative-voltage that would zap your delicate electronics), kickback protection (place across your solenoids, relays & DC motors to safely discharge the spikes generated by the coils), general rectification, and more!

These diodes can safely pass 1A average current continuously, can protect against up to 50V reverse voltage, and have about 0.7V drop for typical usage. Check the datasheet for more specifications!