Blu-Tack re-usable adhesive. If you liked play-doh you'll love this stuff. Maybe OK for posters but not for speakers as advertised in a mid-fi catalog.
What’s your vote for the most ridiculous, overpriced, and useless tweak?
My vote: Furutech Outlet Cover 105 NCF $220, with “special crystalline material that has two “active” properties.” https://www.thecableco.com/outlet-cover-105-ncf.html