Hello.

I want to buy filter for lens and wondering about filter size. Is it 37mm?

Thank you

105mm f3.6 uses Series 6 filters with a Series 6 holder that just slips on over the outside edge of the front element. The internal threads of the front element are not for filters.
Site search series 6 or series six and select all the terms to bring up all the threads about the filters and holders.

45PSS wrote:

105mm f3.6 uses Series 6 filters with a Series 6 holder that just slips on over the outside edge of the front element. The internal threads of the front element are not for filters. Site search series 6 or series six and select all the terms to bring up all the threads about the filters and holders.

And there is no way to screw in protection filyer in any diameter?
I just bought series vi hood, and its much larger. So I understand now, I need special adapter(

Measure the Outside Diameter of the front lens barrel then look for a series 6 holder of that size. The Series 6 adapters were available for lens diameters from 1 1/4 to 1 21/32. Use series V for smaller lens, series VII for larger.
https://graflex.org/helpboard/viewtopic.php?t=3324

The actual filter diameter is posted in this thread https://graflex.org/helpboard/viewtopic.php?t=2052

In a filter thread someone posted that a series VI retainer thread is 43mm.

The Ektar 105mm f3.7 takes a 38mm series VI slip on adapter, a very common size that may be hard to find.
http://www.bnphoto.org/bnphoto/KodakEktarsDB4.htm

Series VI retainer thread is 44 mm.

Thank you alla very much