Billy bookcase tall extender (Shirehampton, BS11)

These make the IKEA tall Billy bookcases taller by one shelf. They fit snuggly on the bookcases. I've one narrow and 2/ 3 wider (I've yet to undo the last one). The fittings (attaching bolts) may be available if I can remove them.
The last 2 photos show a) the tall extender in use and b) the bookcase without the extender. I've moved the study, so can't use them any more. These are oak veneer finish I think, not the light beech.

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