True Bed size for diamondback cover?

In search of a diamondback cover. Found one preowned for a 2019 Ram with a 5’7” bed.

The Diamondback website indicates a 5’7” bed for a Tundra Crewmax but a 2020 TRD Pro specs to have a 5’5” bed.

Is the bed-size the same and the added 2” just the top lip of the bed where the cover sits?

Will the 5’7” cover of the Ram fit a TRD Pro?

 

I thought the Tundra bed was 5'6". Anyway, I would say it's unlikely a cover for a Ram would fit.

 

The Crewmax bed is 66.7” long...many people round that up to 67”, which is 5’ 7”. A DB off a Ram won’t fit a Toyota, though.

I found one locally for sale that came off a 2020 Ram with the same size bed as my CrewMax. The seller kept insisting that it would fit. I sent an email to Diamondback about it, and they were very quick to reply that it doesn’t quite fit correctly because of the “specific dimensions and taper of each truck bed”. I replied to the seller that they said it wouldn’t fit, and he said, “yeah I would expect them to say that. They just want you to buy a new one.” I told him that there probably are subtle differences for different trucks because the thing is designed to be watertight. I also told him he should probably change the language in his ad that makes it seem like it’ll fit any half-ton shortbed. He never did.

 

I actually tried to fit a DB from a 2020 ram with the short bed. It sticks out in the corners by the tailgate by about half inch or so. Because the top of the tailgate is curved and therefore thicker towards the middle, so the rest of it seemed okay. It looked okay but may not be as water tight. I bought one made for a tundra for better fit.