I broke off one of the rubber feet on one my Micropros somehow and I decided to try spikes. Problem was that all the spikes I researched needed for you to do some drilling of larger holes in your sub for the socket part of the spike to fit Too much of a hassle. I called Polk and they said the threads on their sub feet was 3/8". I saw these on Parts Express, ordered them, and they work perfectly in the sockets already in the sub. At first, I though they didn't look cool enough but after I installed them on my subs you can't see them anyway. They work perfect! Just thought I pass this on. I assume they'll work with any sub posts or spikes that are 3/8"