Scott: It was the outside cylinder, not the small tube that the ink is held in. His looked a shade larger in diameter than Bear Perkin's, which looked to me to be only a cylindrical piece of small, red plastic, rounded @ both ends.
I realized I wrote 1/4" clear tubing. Afterwards, when thinking about it, it had to be a tad larger in ID, in order for that homemade piece to fit...maybe 3/8"?
His looked rougher (probably due to that sealer he coated it w/) & it was a darker red color than Bear P's, but the price was certainly better!