I need a turntable for my next layout (HO). I want to scratch build the ATSF roundhouse at Redondo ( http://atsf.railfan.net/structures/rhredondo4.jpg ). Even though the turntable at Redondo is 120' and my turntable must not exceed 90 scale feet, I want to build it the same style. To make construction easy and to have a perfectly rounded pit, I ordered this MDF wood ring at an online store for car hifi products. pennsyrrfan found a source for these rings in the US: Able Audio . Thank you, Paul. The online-store in Germany: CHP car hifi produkte Online Shop The inner diamenter is 11 1/2" and it is 3/4" thick. That makes a shallow pit of 81 1/2'. It will be just big enough for my Mikado.