[Paul R.]

I’d say the inside diameter needs to be 1/8” to 1/4” depending on the diameter of the “string”. 1/4” would be very heavy, so 1/8” for lighter string and 3/16” for heavier string would probably “do it”. I was looking at some brass tubing that has a wall thickness of approx. 0.020”.

(That tubing was actually metric: 4.5mm O.D. / 3.5mm I.D., and also 5.5mm O.D. / 4.5mm I.D.)

Thanks!

[MomwithHope]

OK those specs help.