There are two kinds wheels,one kind with total two wheels,can't climb the stairs,it is flashing wheels,the number 1,2,3,4,5,6 and 7 are two wheels style,



the other kind with six wheels,can climb the stairs,not flashing wheels,the number 8,9,10,11,12,13 and 14 are six wheels style.



Number 1,2,3,8,9 and 10 size about 40*30cm,normally suit for grade 1-3
Number 4,5,6,7,11,12,13 and 14 size about 44*33cm,normally suit for grade 2-6

When you order,please kindly pay attention to the above message.