I was hesitant to buy these when they appeared on the site, so I waited and decided to buy them after some time. They have two sizes one on each end getting bigger and bigger, I currently use the 3rd sound which isn t huge but isn t too small either looks to be roughly 6mm in thickness. The case appears to be leather but I m not 100% sure if it s a Polyurethane leather or Real Leather. Onto my use, I clean the bar every time before I ll be using and then wipe down with alcohol, I use the Muko lubricating jelly but it causes a tiny bit of stinging for me might be because it s Preservatives is (Methylparaben & Propylparaben) I have a sensitivity to glycerin and Parabens in lubricants. I would recommend this set for beginners because it s got the smaller diameters for starting off, from the looks of it I don t think I ll be using the Large Sizes. Overall I m glad I bought these.