Belfast Print Online supply NCR Triplicate Books for receipts, invoices, order forms, stock control etc. with 3 sheets per set. These come in either A5 (148 x 210mm) or A4 (210 x 297mm). They will include a cardboard insert which is attached to the cover. You can choose if you want the spine either on the top or the left hand side, whether you want your books numbered in one position in sequence and if you need holes drilled where the spine is located.