Guys, this is part of the issue I am asking about in my other thread...

Search ebay for 3AG fuses.

Too much chance of a substandard device.
The fuse is the first line of defense for the amp and speakers

Digikey, Grainger, Mouser, McMaster-Carr
Fuse Manufacturers | Littlefuse, Bussmann, Mersen (fusesunlimited.com)

The extra couple of bux for shipping if you can't buy local is cheap insurance. Buy the exact required fuse. If it goes, there is a problem with the amp. Get it fixed.

In more than ½ century in HiFi, I've never replaced a fuse for failure.
Several because a manufacturer scrimped and installed no name crap.

As normb said, if you have a spare, you'll likely never need it.

Luckily for me I am the original owner of the amplifier so I don't have to worry about someone else previously changing the fuses to something incorrect. Sadly, one of the many benefits of the Internet Age was NOT helping the smaller, local shops. We had a great family chain here in Dallas that lasted decades.

Now, what you mostly see in brick and mortar stores are "Home Theater Studios" who aren't particularly interested in anything you have to say just how much you're willing to shell out $$$ in the hope your Media Room sounds and looks like an XD 3D theater.

stereoisomer,

I have the B&K ST202+ Owners manual and it states:

• Main A.C. Fuse    8aSB
• Speaker Fuses    4aR
• Rail Fuse             4aR

Also the gold label on the back of the chassis also states 8aSB

You might consider that the mains power socket that you are using, assuming you are in US domestic residence is generally rated by your city's Electicial Code is 15 amps, do you really  know what you are doing here?