eHow - Hobbies, Games & Toyshttp://www.ehow.com/guide_11-http://www.ehow.com/guide_11-hobbies-games.html.htmlwww.ehow.comMount Centering Rings for Building Model Rocketshttp://www.ehow.com/how_4412894_mount-centering-rings-building-model.htmlLearn how to mount the centering rings to build a Big Bertha Estes model rocket in this free model rockets video. Published on 7/8/2008