Cacafeugo may have more information on Guard Dog Security and the Harm and Hammer If so, I'll defer to him, but the only review of the product on Guard Dog's site said that the product was difficult to deploy and fairly fragile. While the product specifications state it is 18% OC, it gives no indication of the capsaicinoid or SHU levels. While we debate which of those is more important, we have no idea of what that eighteen is a percentage of.
Absent further information, I'd go with one of the better known OC manufacturers such as Sabre Red or Fox Labs.