Aliexpress
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Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
Coupon (5.57 USD): aff7off
(CouponsFromChina.com tip: apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): 30%hld, 0404digoo, 3C11, BGDC11, affiliate6
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Here is price history (for all/most countries) for DIGOO DG-C11 Hygrometer Thermometer.
Price records source(s): Banggood
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You can set price alert (for Banggood).