The swivel range is constructed using female and male parts. 173F is common to all combinations. Lugs on fittings sizes 1 to 5 have the same dimensions, and sizes can be mixed if required, ie: 173F-1 with 173M-4. In addition to being used with 173F to make the combination, all 'M' fittings can also be used to secure various typse infill in place. Warning: An entire structure should not be built just using swivel fittings. Manufactured to BS EN 1562 1997 Galvanised to BS EN 1461 1999.