$10.99 – Battery: 3V(CR2450);, Sensor: 47X27X13.5mm, Wireless connection: Zigbee3.0;, Material: PC;, Magnet: 32X15.6X13mm, Dimension: .
I have checked all old coupons and price is $10.99 for SONOFF SNZB-04-ZB Wireless Door/Window Sensor (in Banggood). Price history, coupons and price alert are available on this page. Do you want to know what the best price is?
Latest coupon and price update (UTC):
Banggood ($10.99)
Banggood warehouse is located in China. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood. I think you want to know if the price is good. From what I can see this price is higher than average price ($8.26).
Link: Banggood product page
Price: $10.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): BGSONOFF15, BGSNZB04, BgcLuBofErtA10, BGSONOFF16, BGSTHO15, BGHONEY2110, BGSHOM15, BG7fca50, 13f142, BGSHE15, 6GSGIT, BGSmart6, 8Couponsde, MVC8SPRING, 8BGwbg2204, 2203ActiesNL, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, BGJUNEGSG9, BG15Sonoff, TTSUMMER8, Cuponation9, 9OFFSUMMER, BG8745ca, BG9ded82
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – SONOFF SNZB-04-ZB Wireless Door/Window Sensor [EU] ($-3)
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for SONOFF SNZB-04-ZB Wireless Door/Window Sensor is here. The lowest price was: $5.57.
Price records source(s): 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)).