There are a ton of choices. Tone bars, with the finger groove on the top….metal round bars, Solid glass bars, spark plug sockets…you name it.
I use none of these, but instead opt for the lightweight thick walled dunlop PYREX hollow slide….yep – fits on your finger for standard slide playing.
Why? I like ’em light…I also like to be able to see thru the slide. Acoustic you can’t get the same tone as you can with a heavy bar – but I find playing electric, I prefer the pyrex.