Is “Kos کوس” reliable for distance of journey?

             Is “Kos کوس” reliable for distance of                                             journey?

 “Kos” (an unstandardised distance measure ranging from 1 1/4 to three miles) is not reliable for journey as these are small at one place and large at the other. That's why three “Manzilمنزل  (pl.) Manaazil منازل” (a day's journey) are reliable. On land the distance of journey is about 57 1/2 miles. Only that mode of journey will be countable by which one travels.