Durst Horing 72mm to 62mm reduction HL2506 HL2501 Horizontal Enlarger lens board.  this lens board screws onto a 72mm threads on the 2506 turret as well as other 72mm threads.  On the 2501 it threads into the one lens opening. Measure yours.  Message me any questions you may have. I only have a limited number of these Horing's.  When there sold they are gone.