As some of you might know already, the genuine Bussmann fuses purchased from a real distributor are not cheap at all they range between $8 and $20 depending where you get them from.
Some of you might have noticed there are Bussmann fuses being sold on Ebay/Aliexpress for way less, around $3 a piece but are these genuine or fake? To try and answer this question I did some tests where I compared a couple of genuine DMM-B-44/100-R and DMM-B-11A which were sourced from a distribuitor in Germany that gets them directly from Brymen to fuses I got from ebay.
The test included physical measurements like size and weight, the quality of the label printing, testing the fuse at the full rated current while measuring it's temperature, internal resistance and finally measuring the time it takes for the 440mA fuse to blow at 2A and comparing that with the datasheet graph.
The results showed that one of the two DMM-B-44/100-R sourced from Ebay performed exactly like it should and comparable to the genuine ones while one showed a breaking time of over 120ms. If you are interested in the tests performed here is a video of it. Of-course testing on such a small batch of units doesn't provide solid results but these are not cheap so it's the best I could do so far.
My theory is that these are really good fakes but with poor quality control thus some of the units are really bad.
People also suggested in the comments that these could be factory rejects, like if they discover there is a bad fuse within a batch they discard the whole batch and that ends up being sold on ebay.
There is also a third theory (highly unlikely) that they are just Bussmann fuses made for the asian market so they are cheaper because of that.
I am also sending an email to Bussmann to see if I can get a response from them. I would like to hear your thoughts on the subject, maybe comments on the test method I used.