If you're in the market for a Point of Sale (POS) card reader there's a few reasons why I would recommend SumUp.
First, if you order via this link you'll receive a hefty discount, I'm not sure exactly how much, it depends on which device(s) you order and what country you're in. For example, a while ago in the UK, the cheapest one (which I have) was £29 (it still is), but when ordered via the referral link it came down to £14. I don't know if that still applies today.
Second, it had (and still has I think), the lowest transaction fee (in the UK at least). If you scroll to the bottom of the page you can select your country, prices, transaction fees, discounts vary depending where you are.
Third...I get a commission