did u check w/ babies r us. U should always purchase all the parts neccessary at the time even if u do not need them-that sounds about right for the rails to a convertible crib-I am sure u can buy rails I saw at toys r us or even target that go under the mattress, but I think that is for full beds, but would not hurt looking into it. We bought all our rails at the time we bought the crib and my firsts crib actually used the drop gate as the rail so all we had to buy was the full size rail when we convert it to a full size bed :) L.:)