Apologies for the road bike question but what is the silver thing in the cable stop and where do I get one?

I’ve got a Planet-X alu SL frame and the gear cable stops have screw threads so normal ferules are too big. Consulting the web site to see how they manage their builds I spotted what I assume to be a screw in ferule but cannot find one anywhere.

its a barrel adjustor

As above ^^^

http://www.on-one.co.uk/i/q/GXPXCARB/gear-cable-barrel-adjuster-for-road-bikes

Right, that makes sense. Thanks chaps.

Paul

Got them on my roadbike there to, very useful.