8" Subwoofer Speaker Spacers Depth Extender Extending Rings - 3/4" thick - ID: 7 1/8" OD: 8 7/8" - 1 Pair - SSK8XK - Stackable - Perfect For Framing Fiberglass Enclosures

They’re flat, they have multiple pre-drilled fastener widths as you can see in the pic. Also, a blank area to drill your own holes.One masssssssssssive word of caution. If you’re either opening up the pre-drilled holes larger with a drill bit or making your own. Go very slow, especially closer to the edge. Very low grade material that is crumbly (which isn’t an issue for this purpose), it’ll blow out. So slowly increase the bit size from if you’re going larger than 1/8”

They are exactly what I was looking for

Bought 2 sizes of these spacers. The package was immdiately a lot lighter than I expected, and I discovered the rings are made of something like a dense plastic foam. Came with some ugly tool marks on their outside edge, so had to sand them for them to be cosmetically acceptable. Also came with some strange instructions, essentially saying they are prone to cracking (they will replace them for free though) and said I can make a hole in them with a screwdriver (wtf?). A bit strange, but they should work. Honestly for the price I was expecting solid ABS plastic or a polished product. These seem like something you would find in the middle of a production line. Meh...

If you are getting these for 8inch subwoofers they don’t fit unless you grind them out. Not worth it and one one them came cracked

Works great very strong I'm pushing a 1200w rms in this tiny box in a jeep tj needs more space for sub

Perfect! Served the purpose I needed

I installed them per the instructions. Didn’t over tighten. And dremeled it out so my subs would fit correctly. Once I started playing my subs it pushed my sub out of the spacer stripping it and causing a gap. And to top it all off it split in half only seconds after I installed it (as I said before I followed per instructions including super glue to help hold it in place) It’s not worth the money. Overpriced for what looks and feels like styrofoam

I bought these spacers needing just over 1/2" additional space for my speakers. The ad says they are 3/4" in depth (thickness), however, they are truly only 1/4" thick. I thought I was simply mailed the wrong size, so I ordered a second pair. Exactly the same....