Recently, while looking for Parker Frontier fountain pen offers, I came along an ebay offer for the Parker IM rollerball pens. The ballpoint and fountain pen versions of the IM series have never appealed to me and the rollerball pen is always the unloved stepchild in between, but I gave them a try and ordered two of them since they were at bargain basement prices.
The IM Rollerball has a metal body and weighs in at a solid 35 grams (with the refill, of course). Mine has a cool, extremely understated silver lacquer finish and does not say where it was made. The cap snaps shut with a positive audible click giving a closed length of 14 cm and a capped length of 16 cm. I cannot use it well when capped as it becomes very top heavy then.
Usually, I am not the biggest fans of rollerballs, but I made good experiences with the F refills (0.5mm thickness) from Parker in the past and these current ones were no exception. They put down an even line with no skipping or blotching that compares well to a fine Pelikan fountain pen line. I have read that these refills were extremely scratchy or noisy. While there is some sound to them when writing, comparable to a fountain pen with a thin and stiff steel nib, mine (made in the UK) are not scratchy at all.
Writing is effortless and smooth, by barely touching the paper, and I´m glad I bought them. The only thing I would criticize is that the brushed stainless steel mouthpiece is quite slippery. Some people might not like that at all as it prevents indexing your writing tool.
A fountain pen sometimes just does not go well on some rougher papers and the ballpoint tires you easily, so the rollerball might be the best of both worlds if you find refills that suit you. Today, with the abundance of gas-pressure or gel ballpoint refills, oil-based and easy-flow inks, the rollerball will probably become a thing of the past.