1,1,2,2,3,3-hexafluoro-4-(2,2,3,3,4,4-hexafluorocyclobutylidene)cyclobutane

1,1,2,2,3,3,4-heptafluoro-4-[3,3,4,4-tetrafluoro-2-(1,2,2,3,3,4,4-heptafluorocyclobutyl)cyclobuten-1-yl]cyclobutane

1,1,2,2,3,3,4-heptafluoro-4-(2,3,3,4,4-pentafluorocyclobuten-1-yl)cyclobutane

1,1,2,2,3,3,4,4-octafluoro-5-(2,2,3,3,4,4-hexafluorocyclobutylidene)cyclopentane