管狀物件，帶或不帶凸緣，旨在減少摩擦，並在平行於孔軸線的表面上承載動載荷。必須具有可見或可檢測的潤滑裝置，或可自潤滑。總長度必須超過外徑的25%或本體週邊平面之間的最短距離，但直管狀（無凸緣或肩部）物體除外，其承載面僅平行於孔軸線。包括分成兩段或多段，且承載圓週角不超過180度（3.141弧度）的物件。另請參閱襯套、套筒；墊片、套筒；以及墊圈（經修改）。不含：銷、空心。
0.1785 inches minimum and 0.1935 inches maximum body inside diameter, 0.2350 inches minimum and 0.2650 inches maximum overall length, 0.7350 inches minimum and 0.7650 inches maximum body outside diameter, mil-p-79,form tm mil spec all material responses overall material document and classification, paper and plastic phenolic or cotton and plastic phenolic or glass and plastic melamine overall material
