One polished 316 stainless steel 90 degree T fitting with 6 set screws. Size 3 allen wrench.  If you are replacing T-fittings on an OEM rail you may need to cut the rail tubing in order to remove the T-fittings as they will not go around any bends.  If this is required, you can then use to restabilize your tubing.

Note: Locktite is highly recommended to secure set screws