Blue Engineering Bricks Class B 65mm Pack of 400Pack of 400 Wire Cut Perforated Class B Engineering Bricks in blue. This engineering brick is suitable for manholes or where a non decorative wall is required. It has high compressive strength, low water absorption and colours can vary, so not ideal for use where consistent colouring or texture is required. Size 215mm x 102. 5mm x 65mm Brick Manufacturer Will vary depending on location and may include; Wienerberger (Terca), Ibstock Brick or Ketley.