I just wrote up a review of the KPS U-13C Magnifying Eyepiece 1.35x here: https://www.pentaxforums.com/forums/pentax-camera-field-accessories/170646-kp...5x-review.html

I think it's a valuable accessory worth considering if you are looking for a bigger view through your finder. I'm always looking for a bigger view. I've tried it only with the K5. With a few caveats (such as, it's not for glasses wearers), it's like looking through a full-frame finder. Thought someone might be interested.

[Adam]

Nice review! IN the future, I recommend you write some in the accessory database - or even on our homepage, if you're really into accessories!