In line filter suggestions?

[Tx Firefighter]

The purpose of a double flare is to provide a flare surface that is twice as thick and hence less likely to crack.

You're making a flare that's folded down inside itself, effectively making that part doubly thick. It's all about safety.

General rule of thumb for all flared hard lines is, tubing 3/8 and less gets double flared regardless of application. Fuel, brake, hydraulic fluid, whatever.