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So rough measurements but they are as follows
Keeping in mind, It has the tub liner and also the Holden Rubber mat in the back
2100 is length from front to back at the bottom (keeping in mind the tailgate does tilt forward a bit and there is that inner section behind the seats)
1800 is length up high from front to back (from where the top lip is at the front to the back)
450 (but could be 500) is the depth of the tub
1400 is the average width at the back
1150 approx the width where the wheel arches are