They seem alright, for the most part.
A lot of them claim to be loaded with BASF bulk stock, so that should be a good thing. Others may be relatively unknown of the tape stock, or you may have to enquire of the seller for details.
I've not bought bulk tapes like that, so I'm no authority. They seem like they should be alright, and the price is right. Any tapes of this type that I've used have come shipped randomly with various Portastudios I've bought. I seem to remember maybe one or a couple having a "rumble" or maybe slight dropouts,... but I'd not condemn the whole lot on scant evidence such as this.
I've been buying name brand Type II cassettes, traditionally. Though they're phasing out, there are still some good deals out there if you look. I trust a name brand a LOT more, and as long as they're available, I'll stick it out til the bitter end. No doubt, I've bought well over a thousand of them over the last few years.
I'll switch to bulk tapes only as an absolute necessity, when the final axe drops on name brand supplies. I'd stick with tape dealers giving reasonable deals and typically stay away from eBay, but YMMV! Also, be careful about unit pricing and shipping charges. Sometimes tapes might mislead you to a 5 or 10 pack, when really selling a single cassette for that price. Also nearly goes without mentioning, tapes are heavy! Shipping could add up on larger orders.
I'm happy to say I've still been able to source good name brand cassettes for reasonable prices./DA
