The quality of the IV chord in the major scale and if used as such, its tonal center is generally the Lydian mode and is subdominant. If used as a IV chord, all extensions are available.
Triad
Root (1),
Major third (3) ,
Perfect fifth (5)
Tensions
Major seventh (7), Major second (major ninth, 9), Augmented fourth (augmented eleventh, #11), Major sixth (Major thirteenth, 13)
Note that it is generally accepted for a Major seventh sharp eleven to be thought to contain all tensions for the sake of argument unless noted by the composer, arranger, performer, god, whatever..
Examples
Thirteenths included in parenthesis
C Maj 7 #11: C E G B D F# (A)
F Maj 7 #11: F A C E G B (D)
Bb Maj 7 #11: Bb D F A C Eb (G)
I'd like to thank kthejoker for his valuable and practical advice.