Why no GSM value for transparency papers/film? How to use thickness instead

[TammyL-Xerox]

Hello temporally_yours, 

I see no one has responded to this post yet. So, at this point I would recommend contacting your local Xerox Support Department to speak with a Product Specialist for more assistance. Please call 1-800-821-2797.

[temporally_yours]

Hi all,

Sorry if this is a stupid question, but I have searched all over and I can't find any answers.

I have a project that I need to print using transparency paper/film for. The particular laser printer I will be using is the AltaLink C8045. Looking at the specifications for that printer I can see that each tray has a different allowable GSM range (http://www.support.xerox.com/know/en-us/altalink-c8000-series/articles/S2092424.html). Additionally, transparency film can only be used in trays 1,2, and 5. According to that page:
Trays 1&2: 60-256 g/m²
Tray 5: 60-300 g/m² 

For this particular project I would like to print on the thickest (ie sturdiest) transparency paper I can use. However virtually no transparency paper I can find lists GSM at all, but instead lists actual thickness (i.e. 4 mil, 4.5 mil etc). No where on the Xerox support do I see any ranges given for max thickness in milimeters. 

I also can't find any reasoning for why transparency film doesn't often seem to include a GSM value. Would appreciate anyone being able to explain this to me, as well as what range of thickness I may be able to use for this project.