Limited Lenses

[Paul]

Hi   Thanks to all of you that gave me advice on panorama mode, much appreciated.   Another question.   I have a 28-200 Tamron, I wish to upgrade.  I am hoping the MZ-S fits the bill body wise, but I have little knowledge of lenses.   I have read a bit about the limited lenses.  Are they primes only?  What is their construction?  How much?  Optically, are they better than regular Pentax primes? Af speed?  Focal lengths?    Boy am I demanding!   Any info is much appreciated.   Cheers Paul