Not sure exactly what you mean here. All my Centuri kits have either an unprinted,or printed original engine casing for the engine block placement tool. The Thin yellow ones came only in the Late 80s-90s. Not sure if Centuri ever used those.

Anyway,,, the SEMROC version is Not the same size as the Original. I just measured everything. On the Centuri one, The balsa block is 1/8” shorter , the BNC is much less Tapered, tho same length. The Fin Root is about 1/8” longer too. Mostly, the main Body Tube is a Full One Inch Longer ( on the Centuri one).

While they are close, and indeed the Semroc one is a fine example, the instructions say the Original Centuri Bat Rok was slightly Smaller than the Semroc. This is incorrect, and the opposite. It is slightly Larger….. in most every respect.
If anyone needs comparison pics, I can send them.
Hope this helps someone.

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