Used fuses should be fine to protect a power distribution transformer.
I haven't used any of these fuses yet. So, I can't attest to the quality. These fuses are used and there is no way of knowing if they have been stressed in the past. Fuses usually blow as soon as they get stressed. However, when the application the fuses are used in causes the fuses to be stressed a lot (such when used in a motor circuit where the motor has to start several times on a regular basis. The endrush current when a motor starts can bring a fuse close to its melting point and possibly cause some partial melting of the fuse element.) the useful life of the fuse may be limited. I'm using these fuses for transformer protection and not part of a motor protection circuit. They should work fine for me.