16 inch - 18 inch 4 piece Sectional Brick Set Cat No 8170014

For sizes of individual bricks see :-

https://www.ashpanworld.co.uk/16-inch---18-inch-bottom-back-brick-157-p.asp
https://www.ashpanworld.co.uk/16-inch---18-inch-top-back-brick---8170002-152-p.asp
https://www.ashpanworld.co.uk/standard-side-cheeks-pair-for-16-inch-to-24-inch-systems-155-p.asp