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):
Blue (M), Black (L), Head Circumference：57 – 61cm (L) Colors：White (L), Pink (M) Inside Color：Grey LED Number：7 Battery：3.7V 455mAh Consistency：36 hours (Lights On) Standby：180 days Charge Time：3 hours Electrical Parameters：DC 5V / 1A Features: Alarming system plus passive protection. Long standby for 180 hours. Consistent for 36 hours. One button control for three light modes.
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
1. ($56.71): 935bc1
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): a9e2f1, AlibuySH50, 0a4f61, Alibuy91224, LSTR93
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. China – XIAOMI Smart4u SH50 Cycling Helmet White ($-3)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Youpin Smart4u Bicycle Helmet Black.
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)).
