Quiescent current 10uA (max), Working voltage 3.7V, Input power 1.25W (max), Maximum working current 130mA (max), Ambient temperature – 10 ℃ – 50 ℃, Battery capacity 250mah, Charging voltage 5V / 1A, Charging current 250mA (max), Continuous working time (maximum gear) About 2.5h, Maximum output power 0.75w (max), Charging Way USB Charging, Low power warning About 2.5h, Low power off < 3.2V, Charging time About 2H, Material ABS, Charging interface DC charging, Power supply mode Buried polymer battery, Waterproof IPX6. Go down and check coupons out. Remember to check price history if it is available. Best price?
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.
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
1. ($28.22): 00c906
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGBTJU50, BGHU0275, BGBTJUT6, BGFE25ZXY, BGAFF10OFF, BGPFHC01, BGMASE01, BGORALIRRI2, BGitIPX6, BGMA2904, BGAP2713, BGGREE1002, BGMAR2406, BGwhielabel, 13f142, BG10OFFAFF1, BGSEXP152, BGHealth06
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Price history (for all/most countries) for Electric Dental Calculus Remover is here. The lowest price was: $15.99.
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)).