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Message: <blockquote data-quote="Kevin Conville" data-source="post: 1317783" data-attributes="member: 63161">Thanks for the informative post Rick.Here's a specific tidbit from Kowa's site that seems relevant:XD lens:Optical glass with extra low dispersion. Also called ED, HD, SD, UD or LD lens. The lens has been developed as an alternative material to fluorite crystal. XD lens can reduce chromatic aberration, although to a lesser extent than with fluorite crystal.The word "fluorite" is sometimes used to mean optical glass containing fluorite component (fluorite glass). The XD lens is made of fluorite glass. At Kowa, the name "fluorite" is only used for pure fluorite crystal.A rose by any other name...Interesting also that ONLY the 883/884 has a true fluorite objective. The 88mm lens must be driving that. I need to look through one of these scopes <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink    ;)" loading="lazy" data-shortname=";)" /></blockquote>