Originally posted by TER-OR I got a Promaster 28-105 with a film body and was pleasantly surprised at how good it was on my K-5 for the price. It's no stack of primes but seemed quite good at 70mm.
Yes, it's plastic.
I can vouch for this being a great lens, it's made by Tamron, their version was named Tamron AF (IF) 28-105mm 1:4-5.6, and there is also a rebadged version with the Pentax name. I had a Promaster and a Tamron. I gave my Promaster to my daughter and it is usually on her K-x, I sold my Tamron version when I got the DA18-135. But it was a good enough lens that I recently acquired another in a a LBA fueled auction which I haven't tested yet, and a couple days ago bought another in an auction (I must have about 7-8 lenses acquired due to LBA that I haven't tested yet. It is a sharp lens with fairly fast autofocus, plastic, and lightweight. You masy find it in black or silver.