Rabbits can eat rye grass and it is a natural part of their diet just like other types of grasses. This is a healthy, easy to digest grass type that is in line with what a rabbit needs from a nutritional perspective.
If the goal is to feed grass to your rabbit then rye grass is not a bad option at all.
In fact, you should make sure to give at least 80% of the food in the form of grass to your rabbit whether it's this type of others.
The key elements to think about include:
General Quality
Organic or Not Organic
Taste
Warranty: Based on manufacturers default
What's in the box
1 x Block of Rye Grass