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Click here… to search for JETBeam RRT03 Flashlight Extension Tube on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
Coupon (14.22 USD): BGOutlight10
(CouponsFromChina.com tip: 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
Old coupons (from the oldest to the newest): BGTORCH, BGSM30%, BgcLuBofErtA10, BGFLS15, 13f142, BGAFF10OFF, cbrIDgTec, BG10OFFAFF1, BANGGOODSD, BGTorch4, 00c906
(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 JETBeam RRT03 Flashlight Extension Tube.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).