filter size ∅40.5mm, brand new $85 (fairly good AF lens)
A hood was not included, you have to pay extra $ for it.
It is a Pentax lens, but put it here since its small image circle.
The lens uses an aspherical element and inner focusing system,
and the outer ring can change focusing (surprisingly) while AF.

Info > http://www.pentaxforums.com/lensreviews/Pentax-01-Standard-Prime.html