Smooth positive lock action slide, convenient spring loaded lock and release lever, wobble free design when locked. High tensile aluminum profile extrusion 13-3/4 x 8 plate, mounting hole pattern: 5 x 12, fore and aft travel: 6. Swivel spider mount: high tensile aluminum 2-7/8 diameter, plastic internal cup. All stainless hardware. Low profile design allows 360-Degree of rotation and 6 of smooth, wobble-free fore and aft travel. Heavy duty anodized aluminum slide plate has standard 5x12 hole pattern. Positive Lock Spider rotates 360-Degree, internal cup engages in 10-Degree increments for positive stop lock (Secondary twist control offers variable drag adj. and can be tightened to lock in place). Internal Delrin cup provides smooth, Gaul-free operation. Meets ABYC-H31, Type A Standards & Garelick performance standards. Reputation for innovation and skilled craftmanship. Best value for boater's dollar.