I purchased 2 yubikey devices in May I purchased 2 yubikey devices in May, paid for express delivery, and still waiting for the devices to arrive at mine. I have tried to contact them via tweeter and emails but no headway so far

U2F Keys from Yubico I think having this type of security (U2F Key) and replacing other methods is just excellent. Combined with a password manager like Dashlane for example is just top notch and definitely safe from attacks. It's an open authentication standard that enables internet users to securely access any number of online services with one single security key instantly and with no drivers or client software needed. They come in many sizes fit to the users needs, obviously make sure to have a few spare.

Yubico's prompt refund I have a higher import duty issue with UPS carrier for an Yubico order and requested them to cancel after 5/6 days. They cancelled and refunded promptly.

Solid security keys I've owned a variety of YubiKeys since 2014, and I've always been very happy with them, I've only had to replace them either because I lost them or because I wanted some newer features, like USB-C or NFC. They seem to be the gold standard for security keys for a reason.

UK customers - Beware the artificially high shipping fee I placed an order with Yubico. They charged EUR15 for shipping. My order was delivered by Royal Mail Tracked 24 service. According to the Royal Mail website, this cost Yubico GBP3.30 for an 80g shipment weight as declared on the Royal Mail label. This means Yubico have charged an artificially inflated price for shipping (GBP3.30 is EUR3.75, which is substancially less than EUR15)