Description This high quality T6 Machined Aluminum Retract is a drop in upgrade for the Robart 635 series gear. With stronger frames, a larger cylinder and our heavy duty 1/2" trunions, this retract is perfect for aircraft up to 55 pounds. All Hercules Series gear are reversible! Specs: Length – 4.25" Frame Width – 1.13" Depth – 1.25" Frame Rail mount length – 2.225" Frame Rail Mount Width – 2.25"  90 Degree Extension Reversible