Description 15 Series, STAINLESS Drop-In T-Nut w/spring-ball. These parts are 100% Equivalent to the following manufacturers: 15FA3603 – 1/4-20 thread: 80/20 #13018 15FA3602 – 5/16-18 thread: 80/20 #13021 15MFA3804 – M5 x 0.8 thread: 80/20 #13029 15MFA3803 – M6 x 1.0 thread: 80/20 #13032 15MFA3802 – M8 x 1.25 thread: 80/20 #13035 These Drop-In T-Nuts are a great way to bolt items to your 15 Series T-Slotted Aluminum Extrusions. These T-Nuts are made from Stainless Steel and corrosion proof. The spring-loaded ball maintains the T-Nut in position in vertical applications. They can be loaded from the ends or sides of the extrusions.