Ok, now that the marrow bone has been established....what is a good length to have the butcher cut them? Again TIA!

They need to be at least 3"or longer.

Years ago, I had an incident when the bone was about 1 1/2" and had a large hole. One of the pups had it and managed to flip it over the lower canines, and it got stuck. I called my vet and told them I was on my way in. I had to hold her head the whole 20 miles because I was afraid that she would bite her tongue. The vets were waiting when I got there and broke the bone with a pair of bolt cutters. No charge, either. LOL
Lesson learned. Longer bones can't do that.

Thanks Gail! I will make sure they are the length that you specify!

Large beef knuckle bones are great, too. And, no holes to worry about! Not only are the dog's teeth cleaned, but as they gnaw over the rounded portion of the knuckle bone, it massages and cleans their gums, also.