Ergodyne Skullerz 8944 Universal Bump Cap Soft Foam Insert, Protective Hat Liner Inserts

Really thin, doesn't really lock together,

This product will only work well if you are willing to permanently glue it to the inside of your hat. And depending on the size of your head/hat, there will be some large gaps between the wedges of foam.

These are comfortable and breathable and make the solid cell insert easier to wear long-term.

Bought to protect my bald head from repeated head-knocks. Works well but is hot and causes head to sweat. To help I can use paper towel to absorb wetness and cools head. Better to sweat than injure head.

These are the cheapest flimsy pieces of foam. Ill fitting. They do not lock together. One piece has little "cut outs" that do not hold together. Front piece has a little extra that doesn't make sense it's just a waste for all the tabs to not be the same length. The back tab is incomplete for fitted hats instead making that the area to cut to fit. Just buy some foam and get to cutting with the picture of this in mind. 100% not worth my money. Likely my hat will out last this foam. So confused why anyone would rate this well and no one else suggested buying foam or neoprene and cutting it instead. Not close to big enough for XXL flex fit fitted hat. You could also have shoe insoles and many more hat inserts if you bought foam or neoprene to cut yourself. Good luck.