I have 3 sizes of Ruffland kennels, with 4 Labs, three females and 1 male. They all have individual crates in the house 1 Ruffland, 1 Pet Porter that's from the early 90's, and 2 wire crates. None of the dogs go crazy in the crates, they simply go in and lay down.
Large - Have one in the house as an everyday kennel for one female apx 75 lbs, plenty of room for her.
Intermediate - Use two of these for hunting season when I am using a Subaru outback, they fit side by side in the rear with the back seat up. 75 to 80lb male rides in one with no problem.
Medium - have one for when I am using a crew cab F150, an intermediate and a medium will fit back to back longways across the rear area of the cab with the rear seat folded up. Two of my females have no problem fitting. 65 to 70 lbs.
Taking the truck one day, I opened the rear door with the medium to load one of the females. My male wanted to make sure he got in the truck, jumped in the medium turned around ready to go. Got him out and he jumped right back in turned around and looked at me like "lets go" length wise it was a little short for him, paws were hanging out. Got him back out, walked him to the other side of the truck to load him in the intermediate.