This is a custom ported enclosure that I  made to fit a DC Audio Level 5 12" subwoofer.

This one pictured was made of 13-ply Baltic Birch and will includes a countersunk terminal plate prewired.

I can build you an enclosure very similar to this in MDF or Baltic Birch. Picked up locally at my shop, or we can arrange for shipping. 
Please let me know which subwoofer this is for, or list the desired cutout diamater when ordering. Thank you!