H metal adaptor (ie to make it fit into a 13mm drill chuck)
This is only for the Commercial THD range of Power Planters as they have a hollow tube where you insert this adaptor to use it on a regular drill chuck.
When you purchasing a Power Planter 428THD 528THD 728THD you will need to also purchase this adapter.
On the NON-THD units (428H, 528H, 728H) the part that can get damaged over time is the hex end that goes in the drill. Rather than replacing the whole Power Planter, on the THD models you can just buy a replacement adaptor.
The rest of the Power Planter range do NOT need this adaptor