The lens casing is 212 x 190 x 52 mm according to my own measurement. To this comes the front plate with the handle and it is 219 x 55 mm and extends 39 mm outwards ( from the casing to the outer end of the handle ). All condensers for the Durst 138 have the same outer size. Only the size of the lens differs. They go from the smallest one ( 85 ) with a tiny litle lens on the bottom plate to the big piece of glass that almost fills out the entire casing of the 240 . I measured the bottom glass surface of the 240 and it is 194 x 158 mm . I hope this is of some help. Good luck.
HI K-G
Thank you very much for the information, last week I got a production in 1978, the Pearl River enlarger, looks like the DURST L138 imitation. But it is a pity that matched lens lost, only a broken 180MM lens, so I want to use DURST L138 240 lens to match, but looks like DURST lens is relatively large.
Thanks again!
Depending on where you live, I send you two different links to suppliers of new condensers. It's Durst Pro in the USA and Kienzle in Germany. New condensers are a bit pricy so you may find something less expensive on e-bay or similar sites ( perhaps under Classifieds here on APUG ). Good luck and hang in there. The Durst 138 ( and I suppose also imitations ) is a wonderful enlarger.