Follicle size on letrozole

Sophie • Baby 2 on the way
I went in for a follicle ultrasound today cd 11 and had 2 follicles measuring 11 x 11 and 12 x 12.will any of these follicles grow to 18 mm ??i am going back again on cd 15.i was taking letrozole 5 mg on cd 2 - 6.