For sale is a Sigma 17-50 f/2.8 EX OS HSM lens in the Sony Alpha mount, in pristine "like new" condition. The lens belongs to Sigma's premium "EX" range and the build/quality reflects that.
The lens has "OS" (Optical Image Stabilization) and allows upto 4-stops of handholdability and when using it on a Sony/Alpha APS-C body, you would need to switch off the in-body stabilization. The lens also comes with Sigma's ring-AF-motor (HSM) but like with a couple of their products, does not allow DMF.
The optical in-lens stabilization prevents cameras like the A55/33 from heating up quickly when shooting video (when using the in-body SSS with video, the sensor heats up in around 6 minutes), while allowing "stabilized" hand-held video and stills shooting.
The lens was purchased a few months back, from B&H, and is in pristine - like new - condition. It also has the remaining manufacturer's warranty.
The lens is fully compatible on the SLT A55 (which I also have) and costed $669 brand-new.
The B&H link (from where I bought the lens) is as below:
Click here for B&H link
Sale Price: $475 (shipped/paypalled) - shipments to lower 48 US states