For macro and close-up photography. This tube will fit all 500-series bodies as: 500C, 500C/M, 503CX, 500EL, 500ELX, 555ELD, FlexBody, 553ELX.etc. by fitting this tube on those bodies the tube ring will be very tight against the release button (plastic collar, so actually tube will not be touching the release button) making it very tight fit but it's possible and it will work fine.
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