SizeAvail is a Boolean property used to indicate if file size information is available in the Size property for the collection item. 

SizeAvail is updated when the registered ListParserClass for the FTP client is used to examine the content in Data in its' ParseLine method. SizeAvail will contain False when the remote file system does not provide file size values, or when the expected listing format does not contain a recognizable marker for the value. 

Use ModifiedAvail to determine if last modification date and time values are available for the collection item.