Why is a echo-request ping packet 84 bytes in the log of iptables?

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http://unix.stackexchange.com – When I log the length of a echo-request packet, iptables -A OUTPUT -p icmp -m icmp --icmp-type 8 -j LOG I saw the length was LEN=84, but in wireshark, the captured packet size was 0x60, why does it differ? (HowTos)