They came with hard rubber plugs. The plugs were used when you had to hold stubby work. The plugs went in the back of the collet and prevented the collet from clamping at funny angles. I have a Jacobs set and plugs. Can’t say I use them much, not at all in the last 20 years. I like my Buck chuck too much. It chucks just about everything I have to hold and I can center the part dead on. But would I sell the Jacobs set…NO. If you don’t have a set yet, then get it! You never know! Don’t forget, you will also need the collet holder/chuck, or make one…Dave.