I pocket carry a SOL Slim Rescue Howler. It isn't the loudest but is compact. Being compact makes it easier to carry (and more likely to be on me when/if needed.

I used to carry a SOL Rescue Howler with a metal slip ring. I found that the slip ring rips off the whistle since there is a weak joint right where the slip ring stresses the plastic. After two failures, I gave up on them.

Thanks.

Conway Yee