D-Line is DGA’s baseline, and DGA writes it as DL or D-Line depending on where you look. It’s the tacky, opaque, inexpensive blend the brand puts its putters and approach discs in.
Baseline plastic is for grip and beat-in. D-Line holds well in the hand wet or dry and loosens up with use, which is why DGA sells its putters in it.
It’s not a driver plastic. It scuffs, and the flight moves, and that’s what you’re paying for. For durability DGA has ProLine and SP.