Service life: more than 500 cycles, Output: 4.2V-5V, L code: 41-46 Euro code, Input: AC/100-240V / 40-60HZ, Battery capacity: Left: 2100Mah / right: 2100Mah, Voltage: 3.0V-4.2V, Number of codes: , USB charging, M code: 35-40 Euro code.
Check coupons or create price alert down below. 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 and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($17.99): BGab7c86
2. ($42.49): BG75597c
put item in your cart and apply coupon code there 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): BG932cf6
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for USB Heated Insole Foot Warmer With Remote Control. The lowest price was: $17.99.
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)).