Xiaomi Mi Band 4 CN Smart Bracelet (Banggood, Aliexpress: Charging Time: About 2hours, Resolution: 240*120pixels, Standby Time: About 20days, Bluetooth Version BT 5.0, Using time: About 7days, Size: 0.95 Inch, Type: AMOLED, Battery Capacity: 135mAh (the best price with coupon)).
Just check coupons out (with price alert and history). You probably want to know what is the best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. Only one coupon available!
Link: Banggood product page
1. ($29.69): band10
this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGeu123, BGmib4Andre, TTxBG10, BGmiband4cina, BGYAmband, BGmiband4grsd, BGBANDPL1, BGktechmib4, BGlskdeimi, BGM43C, bgcn4, BGletni4cn, BGplmiband4, BG3CSUM, BGM4d1, BGNApb05, BGM4FX, BGMICN4, BGDQMI4CN, AFfbG10, BGM428, BGM427, 502C6B, BGBAND29, BGPL11BAND, BGBFAFF2019, BGPro19, BGXMI4, BGNYMI426, BGVDay10%off, BGM426, 88c16e, BGMI4NOVOPRO, BGBGM426CN, BGAFF10OFF, BGMB4M, 9dbbc6, BGM4JL, BGM424, BGEEMIBAND4, BGM42399, bgshOOp10
(these coupons are old, so probably won’t work)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Mi Band 4 CN Smart Bracelet. The lowest price was: $17.87.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).