1″. Dissipates frictional heat – Over five times more thermally conductive than flax and PTFE. Grease-free installation – Self-lubricating and conformable, easy to install and remove after use. Virtually eliminates shaft scoring – Stays pliable, never hardens or becomes abrasive, even at high shaft speeds. Leakage practically eliminated – Doesn’t shrink, keeps bilge drier and free of oily contaminants. Lasts over 5 times longer than other packing. 10# Box.