Not really Bunkie mattresses are essentially the same as any other regular coil spring mattress. Steel coil springs, foam padding, and fabric. These mattress are available in the 2 standard mattress sizes for bunk beds, twin and full.

Most people probably trust they are getting something special when buying a Bunkie mattress. The truth is bunkie mattresses are usually nothing more than a cheaper coil spring mattress that is traditionally sold with a matching boxspring. Since bunk beds don’t require box springs, the Bunkie mattress typically rests on a Bunkie board. The mattress may also rest on steel slats that are spaced very close together so the mattress will not sag.
Couple pointers when shopping for a mattress to use on a bunkbed; at this level of mattress shopping coil count is important. Mattresses are not very technical at this level, so the little things matter.  If a mattress uses more coils you can safely assume that you are getting a better mattress. Another thing to look for is that the mattress coils are using a good heavy gauge of steel. The higher the number indicates weaker steel coil springs. Mattress thickness often correlates into more padding and more padding means more comfort for your child. Do not buy a mattress that will exceed the height of the safety rail in order to keep your child safe so they cannot roll out of bed.

In my opinion a Bunkie mattress is nothing more a cheaply built, inexpensive, uncomfortable mattress for your child’s bunk bed, look for better alternatives there are better mattress options available for just a little bit extra cost.