I can find very little information on the diiference in effect between the traditional Sprenger KK and the newer Sprenger Ultra KK. The Ultra has a losenge that 'tilts' forward in the mouth and I understand that the mouthpiece is finer (although it seems to come in 4 thicknesses 14mm, 16mm, 18mm and 21mm). My young green horse has been schooling in the traditional Sprenger KK, full cheek. He's coming along slowly but he tends to lean. My instructor feel that its time to move to a loose ring and in doing so I'm thinking of trying the Ultra. I've looked for some kind of review comparing the two models but I can't find anything. I have emailed Heather at the bit bank about this in the past, but she always just rcommends her own 75% copper content bit Nue Schule and doesn't really answer the question. No doubt she gets so many enquiries that its difficult to give detailed respones. Anyone here have any relevant experience to share?