Figured I could start a new thread here.  I am putting in new seals on my 73 DT3.  
I do not have anything metric anywhere this big and am pretty sure my local hardware wouldn't either.  So order it is.  Metric size of these two guys?  One guess was a 27.  THoughts?

Measuring across the flats will give you the size.

Sometimes the simplest is not always the most obvious! Thanks. 

Im in the process of replacing my right side seal as we speak. I have the clutch plates out. Im at the big nut holding the clutch basket and stuff on. I do not have socket that size either. I measured it and i was going to get a 27 mm for it. Harbor freight has one by itself for impact wrench for $4.5 and they have a set that includes it and many other sizes for like $25. my post shows that my seal was not even pushed into slot. I had a deep well for the primary. I think it was a 19 but cant remember as i had it and do not have to get one. im going to get a strap wrench to try to hold clutch basket as well.

sorry i should have said that my bike is a 1971 AT!C. Not sure if they are same size nuts but they appear to be

I wouldn't use a strap wrench on the clutch basket, it's very easy to break the basket.
There are a few types of tool specifically made to hold the basket, I think DEET (a member here) still sells one that is specific for you bike.
 

I have seen video where the general process is an impact wrench....

These universal holding pliers come in handy with or without an impact.  www.motionpro.com/product/08-0008

They can often be found for $20 or so shipped.

Use extreme caution with any method that even touches the outer basket enough to apply any force to the outer basket while trying to keep the inner basket from spinning.



 

I for sure will try the impact wrench. i just have to get a socket.

Principal, sorry i got into your post.
Mark T, i have a post "new guy from muscle shoals alabama. I have to replace the right side seal. story is in my post with pictures of the seal not seated as well. Someone said that you might chime in on the seal i need to order. They said there might be a better one available now versus the original part. I dont guess i know how to message someone directly on here. Should i just order the normal seal or is there a better for the job now?