No biggie, I'll try to clarify. All Ttech-like carts come with either a silicone O-ring or a stiff rubber band inside. I switch that O-ring or rubber band out with the dental ligature. I shared a link to the site where I've been getting mine. I order the 3/16"diameter medium and 3/16"diameter hard; medium for shading, hard for lining, 3/16" diameter because that's what tension works best for me (1/4" diameter is too big anyway, needle will just flop around)