We do recommend you order slightly more than you require as concrete & clay products can vary from batch to batch in colour and size. If you decide to extend your project at a later date, you may have trouble getting the product when you need it and there may be additional cost involved. Sometimes just a few weeks can mean a new batch is available, which could result in product features changing slightly (ie. lighter or darker in colour – even slight size discrepancies) You will also need to allow for any wastage incurred due to any cuts required.