The 2" 1.6X barlow is back after a complete optical and mechanical re-design. It comes in (2) parts.
Part#1 is like a DP2, housing the lens; 2" barrel with T2 output thread. The lens has been optimized for 55mm backfocus, consistent with DSLR's like Canon and Nikon.
Part#2 threads onto the T2 thread of part#1 for visual use, with the usual twist-lock format. A rubber ring is supplied; it goes between the two parts to prevent un-threading when using the Visual Back.
This has been designed to not change the characteristics of the telescope (eg. a Newtonian will still have coma), but edge spot size has been reduced by 30% over the previous version.