This is a C-shaped spring retainer.  It is used to retain something at the bottom of a drilled hole:

• use a pair of pliers to squeeze the legs together and the part will compress, allowing it to be inserted into the hole
• when released, it springs outward against the walls of the hole and holds itself in place

The model is fully parametric, meaning you can customize this to the size you need and every aspect of the part, including fillets and chamfers are updated.  You can either:

• download the Fusion file or
• click Customize above.  Note: MakerWorld only takes measurements in mm.  So you need to convert if you work in imperial.

Filament:

• I do not recommend PLA - it's the filament that creeps most under constant pressure and will lose its strength.
• PETG is a much better choice.

The print profile is the size I needed.  It's unlikely this is what you need.  The dimensions I used were:

• holeDiameter - 1.25" hole
• holeDiameterSpring - 2mm (extra diameter needed to make it spring)
• wallThickness - 4.2mm (thicker wall makes the spring stronger)  

What I use it for

To retain 1.25" diameter neodymium magnets.  The magnets are inserted from the rear of a panel into a hole drilled almost all of the way through the panel.  Those magnets hold doors to place when opened.  I could have glued the magnets in place, but this makes them removable.  I can change or add magnets to increase strength, remove the magnets when sanding/finishing the panel etc.