You mean what is Euro Bracing. It refers to the brace around the top of a tank.<span style="color: Black">
</span><span style="font-family: Helvetica, Arial, sans-serif"><span style="color: Black">EURO BRACE:
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<span style="font-family: Helvetica, Arial, sans-serif"><span style="color: Black">Euro Bracing is the most sought after bracing style by aquarium enthusiasts. Euro Bracing offers the most accessibility into the aquarium for servicing and decorating.It's open design eliminates any hindrance of light penetration, making it the perfect choice for Planted or Reef Tanks. The perimeter bracing width is approx. 3"W.
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<span style="font-family: Helvetica, Arial, sans-serif"><span style="color: Black">Note: Euro bracing is not suitable for 'hang on' filtration due to bracing width.
</span></span>http://www.oceaaquariumproducts.com/eurobrace.gif