Cat 1 Oliver ( chip ) cat 2 Tango ( Tag ) Within 48 hours , the older cat , Tango , had overcome his fear of the whirring unlatch mechanism. After two weeks , Oliver had managed access just twice. Noticed it was distinctly more difficult for him , so made a quick loop of knicker elastic for a spare tag ( cat 3 ) . This is definitely easier for him and works in preference to his chip. Just in time before major snowfall. Cats have extremely flexible skin so his chip could have migrated further back making latch triggering difficult. So have to award the Petmate 355 a cautious ten out of ten. Bellsie , West Midlands.