this sounds like the method junkies use to filter 'gear' for iv injection. if they did that for im injections, they would be in abscess city. the pieces of rubber are sterile (provided the stopper is still intact), and you likely wouldnt have had any problems. this is why its always good to post before you do something: we've likely done it ourselves or know what to do. get some micron filters and a sterile vial and re-filter. it will be educational.