The 5 Amp Slow Blow (FST) by Master Spas is an exact replacement fuse for your home spa. If certain features of your spa are not working properly, a broken or blown fuse could be the culprit. When a fuse is blown or is malfunctioning, it can cause some parts of your spa to break down or stop working all together. The 5 Amp Slow Blow (FST) fuse by Master Spas allows an increased level of power to flow without overwhelming the circuit. It is long-lasting, affordable and will allow you to enjoy your spa and all of its features.