They are just under 5/8. I believe they may be some kind of tweener tri lite but I'm not too sure. I am nearly 100 percent sure these are Vitro. I have others that seem to be from the same "run" that are definitely Vitro and you can see the progression into these. They are translucent and have a fair amount of clear glass in them as well. The 4th pic shows a line of AV, I believe and the 5th shows that AV after it has moved up to the multicolored patch on the marble. In the first picture, the ones on top have some blue mixed with "black". These aren't in perfect order but you get the picture. There also may be some oxblood in these as well. I'm fairly certain they are early vitro because of the quality of the glass and the clear glass. Also, the last picture, the first marble wasn't in the other photos and has no color on the other pole. Any thoughts?