About the length of my thumb.

Another first at the gig today: a full-sized cockroach. I was more irritated than anything else - "What? Aw, come on, I'm busy here" - when I saw it come out of the box, largely because it wasn't anywhere near me and the room had bright enough light I recognized it for what it was immediately rather than catching a glimpse of small, fast motion right out of the corner of my eye. Now that would've scared me. A moderately sized insect is much easier to contemplate.

I've already taken the policy of tossing out stuff sight unseen if it's moldy or far enough gone, and this just cements the practicality of that.