Stinger RoadKill 3 Piece Foam Rings for 5" Inch and 5.25" Inch Speaker – Pricedrightsales
Foam ring, 4 inch, for a speaker with a cone size of 6,7 cm
Amazon.com: VOFONO Speaker Fast Rings 6.5 inch [4 PCS], Car Speaker Foam Baffles Enhancer System Sponge Bass Blocker Kit for 6" and 6.5" Speaker : Electronics
4x Black 6.5" Universal FAST Foam Rings Car Door Speaker Enhancer System Kit | eBay
Audio System ADSPC1 open cell foam 6.5" speaker rings pair (fast rings – SoundQuality.net
SoundSkins Rings – SoundSkins Global
ResoNix CCF Strips - Foam Speaker Ring Strips For Speaker-To-Panel Coupling - Pair - ResoNix Sound Solutions