This caught my attention last Fall and I made a point of doing gelatin tests, then meeting DDupleks crew at SHOT show. 20ga slug is only 19.5g (2/3 oz) and its velocity is 450m/s (1475fps), so the recoil impulse is relatively light. Since each projectile is CNC machined from steel, its “petals” pivot against pre-set points and open up consistently without fragmenting. Expanded diameter is about 1 1/8″.
Give the miserable performance of generic hollow point slugs in 20ga (shallow penetration with excessive fragmentation) or the commonly available #3 buckshot (again, inadequate penetration), this makes my 870 Youth rather more useful.