They are cheap and they work!
So, step by step. 1) The quality. The sensors are actually good. High-quality housings with a placement marks. The PCB are universal, with possibility of placing a button (K1- for a triggering when the button is pressed). Powered by CR2302. The sensor is not a reed switch, but a Hall sensor (Q3), and the sensing distance is quite decent. 2) The Shop. VERY long delivery even though I paid for Aliexpress Standard Shipping and asked the seller if he will ship, and he confirmed. Instead, he sent by regular mail - I received in two months... As seller said, the shipping method was changed because of the magnets. So, only the good quality of the product convinced me not to claim a dispute for "change the delivery method". Verdict: Product - 5 stars. Price - good. The rest is on the seller's conscience.