How to measure
First, ensure that your microphone capsule is between 18-23mm in dimeter. Then, determine the length you need by measuring from the front-end of the capsule to the end of the grille (vents), and add about 1cm to that measurement to ensure a full seal.
Compatibility (including but not limited to)
Audio-Technica: AT 815ST (BP4027)
Azden: SG(M)-2X (Omni)