A:AnswerGoogle doesn't have anything about a K500 - is that the right model? Best Buy doesn't carry the K575 but the specs are very similar. The K525 didn't come with accessories - just the coffee maker.
A:AnswerThe My kcup 2.0 for the 500 plus series works for the cup, mug and carafe. There is a little, "trigger", that you pull down in the Keurig where the kcup goes. Once you slid it down you put the kcup in and when you take it out it clicks back into place.
A:AnswerI believe one holds 60 oz. of water and one holds 80 oz. also, I believe the 575 has a few more options for the mug size you may choose to fill.