Like tx_tuff said, the D-ring is because the V3.1 is meant to be Luke's green saber that he built before ROTJ. In the original trilogy the lightsabers had D-rings and hung from simple hooks on the utility belt. The covertec wheel and clip thing appeared when they made the prequels, so it's either an older or newer way of doing things depending on your point of view. Lord Vader's saber actually had a ring near the emitter so it could be hung from his belt emitter up for a quicker draw. I bet I'm not alone in wishing there were more D-ring options from UltraSabers, on the Graflex and Chosen One if no others...
Yes yes yes and yes! More D-Rings!
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