What kind of valve is this? Toilet supply to fill valve.

[Jeff Handy]

I have to say, if you had already found that 1/2 inch flare fitting flex supply hose, but it was too short, and did not mention it in your postings here, you were withholding information that we needed.

 

[SkottyG]

It is a 1/2" female IPS x 3/8 male compression straight stop.