Yes, these do fit in place of the rollers and the rollers are put in the extenders. On my machine there is a slot into which these fit, to keep them from tilting inward or outward and I don't see that slot in the roller holders that are glued to the base of your machine.
However, this image posted below indicates that some roller holders don't have the slot and the tabs just grab the outer edge of the roller holder to keep the extended rollers from flipping outward. Obviously the roller holders need to be glued to an exact location in your machine so that the rollers contact the tank perfectly with either the rollers alone or with the extenders.
I also wanted to point out that the roller base that was mentioned is the exact same parts as the roller assembly used for the lift. It is compatible with those roller extensions and would keep the rollers the exact specified distance apart but hands-on testing would be needed to see if the height is correct for your machine.
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