Vik Olliver has posted the above image to the RepRap Project blog. Unfortunately there’s apparently no “permalink” to the specific blog entry, so I’ll just quote Vik’s description:

Adrian is currently printing the first draft of the pinch wheel feed mechanism for the extrusion head. It consists of two interlocking pinch wheels that push the 3mm Polymorph rod down a guide and into the opening in the 10mm PTFE rod… Small holes in the pinch wheels can take metal points if additional traction is required, and the symmetrical clamp should hold the PTFE rod centred.