The Russian 91% v2 is the best made clone of the Kayfun lite so any, and all, parts for the Kayfun lite (and v2) will work in the Russian. I have 8 R91% v2's and have bought many authentic SVM KFL spares and other spares. At FT you won't find it listed under "Russian", everything Kayfun related is now listed at "Lite Plus" and they used to have many items for both.
I just looked and FT is now sold out, bummer.
https://www.fasttech.com/products/3052/10044031/9475300
In a way that is good because I have a much better source for replacement parts with superior machining.
Fat Daddy Vapes, I have bought much from Dennis over the years. He has quality parts made for mechs too. He and his son are great people.
FatDaddyVapes.com - Home of the best vape tweaks and replacement hardware.
Shop:
SHOP
Search for Russian 91% and you want this listing... I have several of these kits...
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He has also been selling 510 BF parts to folks who make squonkers for years. There are many useful items on the shop page.
Another good source for parts is cremedevape. They used to carry every part for the Kayfun lite. I just looked and they no longer carry any parts, bummer.
However, you might want to consider grabbing a Kayfil tool from them. I have one and they work great with the Russian/Kayfun lite.
Crème de Vape Kayfil Tool
"A very simple solution to allow access to the coil/wick in the original Kayfun Lite Plus without the need to drain the juice. Not only does the KayfilTM tool enable easy access to the coil, it also allows quick topping up on the go."
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Hope that helps...