Has a 49mm filter thread.
PENTAX-M PK 135mm 3.5
PENTAX PK-F 35-80mm 4-5.6
SMC Pentax-M 135mm f3.5 Telephoto Lens PK Mount
Hoya 135mm F2.8 HMC Lens BOXED LEATHER Case - Pentax PK Mount MINT CONDITION
Auto Chinon 135mm f2.8 Portrait Lens - PK Mount
PENTAX TAKUMAR 135mm F2.5 PORTRAIT/TELEPHOTO LENS & CAPS PK MOUNT Super lens
