The opposite of a soft pillow/seat can very well be a firm pillow, according to the preference of the user.
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Side sleepers do better with a firm pillow, stomach sleepers are best suited for soft pillows, and back sleepers should try a medium-fill pillow to support the natural curvature of their upper spine.
http://www.thecompanystore.com/pillows
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Extra Firm Pillows (2 Pack)
This Perfect Sleeper pillow is filled with premium firm fiber for extra-firm support that's also comfortable. Its premium polyester fill provides gentle cushioning for your head and neck. This pillow features a 300 thread count cover made from ultra soft, durable 100% cotton.
https://www.serta.com/mattress-accessories/pillows/perfect-s...
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Choose from soft, medium, firm, and extra firm feather pillows. Each is made in the USA from 100% Hungarian feathers and down.
https://www.downandfeathercompany.com/pages/feather-pillows-...