Welcome to SaleHoo!
I haven't personally used DevilWear but they are a verified SaleHoo supplier and they have a 5 star average rating from other members. You can find out more about them here:
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They are a well-established company and they also accept safe payment methods such as PayPal and major credit cards, meaning you can get your money back fairly easily if something goes wrong.
If you want to be absolutely sure, though, inquire about their products' authenticity or request for authenticity documents before you go any further. You can also purchase a sample before bulk ordering to ensure that their products meet your expectations.
All the best!