The new Caterpillar 309 CR Mini Excavator, also announced as the "Next Generation Design" or short “Next Gen” Caterpillar Track-Type Hydraulic Excavator is the successor to the "D" Series, but because Caterpillar has changed his machine type numbering and stopped adding the successor letter it just will be released as the "309" Series.
Of the 309 Series Excavators, only the Caterpillar 309 CR "Next Gen" Mini Excavator has been released in 2019 by Diecast Masters in 1:50th scale.