Mast T-Base - Adjustable is a mast or boom service fitting for compatible Seldén spar systems. A range of adjustable mast steps. Please use the specification sheet in the ATTACHMENT tab to make sure the correct adjustable mast base is ordered to match mast section. It is intended for replacement, maintenance or completion of the corresponding original spar assembly. Because Seldén has used several mast and boom sections over many years, check the existing component, section profile and fixing dimensions before ordering. Where an article number is shown, use it as the primary identifier and do not assume that a visually similar fitting from another spar section will be interchangeable.