change field length on multiple forms

Hi
I am using multiple contact forms on my site. I am trying to change the field length of text fields in a specific form. I have added css which changes the text field length in all forms, I just want to change one.
How do I add css to change just one form?
Presumably I include the specific form ID in my css. Tried but failed so far..
Any ideas?
Thanks!

https://www.ads-software.com/plugins/contact-form-7/