K40 or K-40 may refer to: BMW K 1300 S (K40), a sports motorcycle from BMW Motorrad , a corvette of the UK Royal Navy , a destroyer of the Israeli Navy , a corvette of the Indian Navy Piano Concerto No. 3 (Mozart), by Wolfgang Amadeus Mozart Potassium-40, a radioactive isotope of potassium Redmi K40, a smartphone Toyota K40 transmission