This fits Shearwater PETREL WITH RADIAL SEAL. Please take note of the type of cap you already have, there are 2 types and they are not compatible with each other. SEE BELOW ON HOW TO IDENTIFY THE TYPE YOU HAVE.
Identification
Chassis
A radial style chassis has the letters “RC” (radial cap) etched on bottom.
A crushed style chassis does not have these letters.
Battery Cap
The radial cap has an extra step at the back of the cap.