$13.99 – Material: ABS, , Output Voltage: 3.7V / 10A, Color: Gray/Green/Red, Idling Time: 2 hours, Package Weight: Approx. 183g, Input Voltage: DC 5V USB, Polishing Working Time: Up to 1 hours, Choose：Standard Model / Deluxe Model （optional）, Collet Chuck Diameter: 0.5-3.2mm, Rated Power Input: 10W, No-load Speed: 5000/10000/15000 r/min.
You can get USB Charging 10W Grinding Machine for $13.99 using coupon code (in Banggood). Go down and check coupons out. Remember to check price history if it is available. Do you want to know what the best price is?
Latest price update (UTC time):
Banggood ($13.99)
Banggood warehouse is located in China. I can’t find any active coupons for this product in Banggood. Is it cheap? Hmmm, price is higher than average (which is $13.32 right now), so better set price alert down below…
Link: Banggood product page
Price: $13.99
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BG589b2e, BGPT07
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
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 USB Charging 10W Grinding Machine is here. The lowest price was: $12.99.
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)).