A cill sits underneath the frame and is there to drain rain water away. If you have an existing Cill this would normally be replaced unless its concrete. Ours are 30mm high, and we offer three different sizes:
85mm – With a 15mm projection, this is used when the frame is fitted forward in the reveal
150mm – With an 80mm projection, this is the most commonly used size
180mm –With a 110mm projection, this is used when the frame is fitted further back in the reveal
IMPORTANT: Enter ‘overall’ sizes including add-ons and / or cill if required.