Add the adjustable convenience of the Tigress 1.5 T-Top Clamp-On Outrigger Holder to your boat without adding any holes in your hardtop or gunnel. To install, drill a 0.25 hole into the IPS-schedule pipe of your T-top and clamp on the holder. 1.9 clamp size. 1.5 holder size. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Outriggers/Accessories.