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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. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
Coupon (21.47 USD): ADMITAD2212
(CouponsFromChina.com tip: apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): e2bcea, elec, BG3dgeek3, AFfbG10, 502C6B, BGBFAFF2019, BGE13, BGAFF10OFF, 13f142, bgshOOp10, BGELIG0920, BgcLuBofErtA10, BGCuponation10, BGHONEY2110, BGd0b05d
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Do you need price history chart (for all/most countries) for Practical 6-36V Auto Leveling Sensor for 3D Printer? There we go.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).