Here is my complete set of these great Pentel Slim Rollers from the 70s to the 90s. These are by far my favorite pentel rollers. Starting on the left are the R-3s. There are five of them and there are slight variations in the ones made in the 70s verses the 90s, also there is a slight variation in the ones sold in the US, Europe and in Japan. Next are the green, black, blue and red R-4s. Then the gold brush R-6 followed by three striped R-7s. Three sterling silver rollers followed by the gold R-3000. The difference in size on some of them are the refills. Most have the standard MG8 refills while others have the Ceramicron refills. In the standard MG8 only black is available. In days past you could also get refills in red, green, blue. Add them all to your collection.