Necessary, the nuts are 13 mm and 17 mm across flats, but as small as possible is as good as possible, it is up to 16 mm, but other manufacturers also made this product. I thought it would be nice if there were for 13 mm to 17 mm if possible.
I was able to break it without problems though the nut was cracked or suspicious. Just break the hexagon nut fastening the breaker immediately. It became difficult to use when the tip turns round. Currently I use it with holding by hand.
I thought that it was convenient to break the old vinyl house but purchased, but the plates with nuts were all bent inwards and could not be used. If the ring is thin 2 millimeters or so, it may have been a comfortable work