Bearing: 2BB, Weight: 20.3 g (0.72oz), Connector Wire Length: JR 220 mm, Stall Torque (4.8V): 3.2kg.cm, Dead band: 2μs, Motor: coreless motor, Model: PDI-2004MG, Brand: JX, Potentiometer Drive: Direct Drive, Operating Voltage: DC4.8~6.0 V, Operating Temperature Range: -10 to + 60°, Operating Speed (6V): 0.08 sec/60°, Dimensions: 23X12X27.6 mm, Working frequence: 1520μs / 330hz, Operating Speed (4.8V): 0.09sec/60°, Stall Torque (6V): 4.2kg-cm.
You can create price alert here, copy coupons and view price history. Let’s see what best price is ATM.
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. ($19.03): BGMatt2022
2. ($19.03): BGToys8
paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): BG2e3f59, Cuponation9
(there’s a little possibility that old coupon will work)
Price history and price alert
Check out price history chart (for all/most countries) for JX Servo PDI-2004MG 4.2Kg Metal Gear Digital Servo. The lowest price was: $16.99.
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)).