Provided is a tube comprising a tetrafluoroethylene/fluoroalkyl vinyl ether copolymer, wherein the tube inner surface has a surface roughness Ra of 5 nm or less measured by atomic force microscopy (AFM) with an evaluation length set to 3 m, and the tube has an amount of metals eluted from the tube inner surface of 0.30 ng/cm.sup.2 or less.

A drainage plate (10) for an extruder assembly including a body (12) having an inner edge (14) and an outer edge (15). A seal portion (24) of the body extends radially from the inner perimeter toward the outer perimeter. One of more drainage features are located radially outward of the seal portion. The one or more drainage features extend an axial depth into the body such that a first thickness (t1) of the drainage plate at the seal portion is greater than a second thickness (t2) of the drainage plate at the one or more drainage features. Methods of manufacturing a drainage plate and manufacturing ceramic articles are also disclosed.