We have used a few of these over the past few years and have found that many electrical problems are related. Do not hold the fuse, vibration or movement can break the electrical connection. They may be suitable for fixed installations but are not suitable for trucks, boats or trailers. The rest was just thrown in the trash.
Pros: Inexpensive and easy to use. Cons: The first one I used (for the microwave fuse) completely melted and fell apart when the fuse blew. I assumed this fuse got very hot when it blew, so I replaced the fuse and holder. Now I find that the second holder is also melted and bent, although the fuse has not blown. My guess is that this plastic mount just isn't made for high temperatures.