Ritalin SR is a moderately slow release version of methylphenidate. It has a less than stellar reputation for being reliably absorbed and actually working, so if I need to use it (almost always because of drug coverage issues), then I will test with another methylphenidate product first, then switch to the SR to save money. Duration, when it works, is 5 – 8 hours. If it does work, it’s a perfectly good option. It comes as a 20 mg. capsule and the maximum dose I typically use would be two caps, possibly twice a day.