Thread adapter (YELLOW)

YELLOW adapter in picture above. If you have one, then you know what this is...allows quick-change of filters that have two slots in base. Adapter threads into tub, filter twists and pops off. YELLOW one is coarse-thread (PAD 2S, ACME) Sometimes called "twist-lock" filters. Used on numbers 1,3,3MB,9,9MB in photo above.