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- They comply with Building Regulations Document L England for improved thermal insulation.
- The 4mm perimeter seal of Slender Fit Double Glazed Units enables them to be glazed into 7mm deep glazing back rebates found in most sash windows.
- The smaller cavities between the glass reduce the required glazing width rebates and enables slimmer sections to be used.
- They are the only double glazed units that can be glazed into most standard glazing bars of a sash window.
- They can be glazed into most existing single glazing glass rebates.
![cottagewindowbox cottagewindowbox](http://www.slenderfitwindows.co.uk/wp-content/uploads/2011/07/iStock_000011707703XSmall-1.jpg)