Fighting bro 3.0s V2 titan enhanced split gearbox

Hi all,
I’m on a tight budget and recently purchased the Fight Bro drop in box to install in my K1 Kublai. The gearbox does fit, although the receiver needed some slight modifications to allow it to slide enough to split open without having to pulled the whole gearbox out. My issue is I didn’t realise this gearbox comes standard with a thread less spring retainer. I’m now left wondering how the buffer tube bolt is meant to attach to the receiver. Any past experience or ideas on how to get around this would be appreciated. Cheers

You can take the spring retainer from your Kublai gearbox and use it on the fb gearbox

Thanks mate, I’ll try that