There are lots of different types of hay on the market. What you’re looking for is a good quality hay. The hay shouldn’t smell mouldy & shouldn’t be dusty. If it is leave it.
I personally use meadow hay & it has worked well even on the reluctant hay eaters, but any other hay can be used. Some people mix them & find the different variety encourages their bunny to eat more hay. I purchase my hay in bale form, it has been specifically cut for bunnies. Some people say that baled hay straight from a field could have been contaminated by wild bunnies & therefore disease could be passed on. Although this is a possibility, I know wild bunnies do not like going into long grass & I have fed my bunnies baled hay from a field for over 30 years & have never had a problem.
The only hay that is not suitable to be given on a regular basis to an adult bunny is the Alfalfa hay. It is too fattening, as it has a high protein level, it’s often used as an animal feed. That said, it can help any bunnies that are needing to gain weight. It is also good to give to growing bunnies.