The Beseler 23C Lens Kit included everything to make your 23C III-XL enlarger complete for printing 35mm film. It includes a Beseler 50mm f/3.5 Enlarging Lens, 39mm lensboard, jam nut and 35mm carrier.
35mm lens kit for 23C III-XL
Beseler 50mm f/3.5 enlarging lens (#8650)
Beseler 39mm lensboard (#80210)
Beseler 23C III 35mm Standard Negative Carrier (#8053)