Wire Core: Copper, Product Weight: 3g, Color: Red, Wire Material: Metal+PP+TPE, Cable Plug: 3.5mm jack, Size: 10.5*5.5*90mm, Type C.
Check coupons or create price alert down below. You probably want to know what is the 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. Only one coupon available!
Link: Banggood product page
1. ($13.20): BG85d5c6
apply it 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): TTxBG10, AFfbG10, BGBFAFF2019, BGCITYADS2019, BGVDay10%off, BGAFF10OFF, bGhOnEy10, BGXMI15, BGdragonBoat, BGSS10%SW, BgoFErTaSchInA10, BgcLuBofErtA10, BG20CHARGER, BGMBCBLE, BGHONEY2110, 13f142, BANGGOODSD
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Here is price history (for all/most countries) for Oneplus Type C To 3.5mm Adapter. The lowest price was: $3.28.
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)).