Younger has broken new ground with the introduction of Trilogy lenses in a Flat-Top 28. This is the first Transitions product to be available in a high impact material in a Flat-Top 28. Trilogy Transitions FT28 lenses are an ideal choice for rimless drill mount frames. Trilogy is Trivex material that has high impact resitance with superior optical characteristics (Abbe value 45) and lower internal stress. Available in adds of 1.00-3.50D; Rx range of -9.00 -+7.00D.