Review on Qty 315MA Fast Blow Fuse GMA315MA by Punk Espinoza

TL DR Version: These fuses will happily handle twice their current rating before they even glow. I couldn't get them to pop until I ran about 800mA through them. They are NOT an exact replacement for the Radio Shack GMA 270-1046 fuses used in the INNOVA 3320 Multimeter, despite claims to the contrary in the reviews and Questions/Answers here. As they currently don't offer two day shipping I'd recommend getting the correct part number from Radio Shack instead for around the same price. Long Version: Let me preface my review by saying that I'm not an electrical engineer. I know enough about electronics to hurt myself or others, but I'm definitely an amateur. I'd be happy to update my review if someone corrects me on any of my findings below. Based on the reviews here and the specs listed, I bought these to replace a blown fuse in my INNOVA 3320 multimeter. But before I entrusted them with my multimeter, I wanted to test that they were within specs. Using my small desktop power supply and a bunch of resistors, I got the following results. I used the power supply in current limit mode, starting at 300mA and increasing the current in 10mA increments, pausing at each step to see if there was a noticeable change. Using a 1 ohm 3 W resistor: * No noticeable change up to about 500 mA. * At 600mA it starts to feel warm. * At 700mA the fuse will glow but not blow. * At 800mA the fuse will definitely blow, although it will blow rather than blow. Regardless of the voltage, but just to be sure I tried again with a 22ohm 2w resistor and a new fuse to see if passing more total power through would make a difference: * 8v, 350 mA - the fuse has not blown. * 10V, 450mA - the fuse has not blown.* 12V, 550mA - the fuse has not blown. At this point I was delivering 6W of power through a 2W resistor that got very hot, so I stopped. Not knowing if these results are reasonable, I turned to an electrical engineering forum. I got the reply that my results might be reasonable, but you really can't know without looking at the fuse's datasheet. So I decided to buy a set of four 270-1046 fuses from Radio Shack (who knew you could still buy some of those online?) and test them against them to see how they fared. I started the first test with one of Radio Shack's fuses and it started to get hot at 400 milliamps. Given my results with Revain fuses, I ramped the current up fairly quickly from a starting point of 300mA, half-expecting it to reach at least 500-600mA before seeing a big change. But at about 470mA it suddenly burst. This is more in line with the behavior of a 315mA "fast blow" fuse (at least in layman's terms). if you spend the minimum for free shipping). And they arrived just a few days longer than the Revain backups. For that reason, and based on my testing above, I cannot recommend these fuses unless you are familiar with a completely different real-world performance. I would strongly NOT recommend these fuses as backup fuses in the INNOVA 3320 multimeter as they protect the 200mA circuit and I would be concerned about possible damage to the unit. Pay attention to my star rating. I'm giving them 2 stars instead of 1 because I don't have a datasheet to know what the true specs should be and because some people might still find them useful knowing their actual performance.