Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Cincinnati Bell (NYSE:CBB) plunged today by as much as 10% after subsidiary CyrusOne commenced its IPO.

So what: The expected price range for the offering is $16 to $18, and the company is selling 16.5 million shares. If underwriters exercise their options, CyrusOne could raise upwards of $341 million. CyrusOne is looking to be listed on the Nasdaq under the symbol "CONE."

Now what: The subsidiary contributes nearly 15% of Cincinnati Bell's revenue, and after the deal's completion Cincinnati Bell estimates it will still have approximately a 72% stake in CyrusOne. CyrusOne had said it wants to structure itself as a real estate investment trust. The pricing range is on the conservative side of what investors were expecting, which may be contributing to the drop.

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Fool contributor Evan Niu, CFA, has no position in any stocks mentioned. The Motley Fool owns shares of Cincinnati Bell. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.