Once you have your binding covers picked out, use these binding spines to keep your documents and presentations neatly bound. Durable construction ensures that your finished document is both fully functional and long-lasting. Permanent spines allow your pages to lie flat to keep them manageable and easy-to-read. Sturdy plastic material will not scratch, peel, chip or discolor for lasting durability. 5/16" spine binds up to 40 letter-size sheets. 19-hole binding spines are designed for any comb-style binding machine (sold separately).Once you have your binding covers picked out, use these binding spines to keep your documents and presentations neatly bound. Durable construction ensures that your finished document is both fully functional and long-lasting. Permanent spines allow your pages to lie flat to keep them manageable and easy-to-read. Sturdy plastic material will not scratch, peel, chip or discolor for lasting durability. 5/16" spine binds up to 40 letter-size sheets. 19-hole binding spines are designed for any comb-style binding machine (sold separately).