Pier Fixing Parts for Plarail 3D Printed

Looking at the texture of those black ones I reckon they are probably made of TPU as opposed to the normal PLA material. TPU is rubber like so could potentially be designed to exert some pressure on the rails from the sides rather than clipping over the top of the edge of the rails which the blue ones look like they do. An interesting solution to a problem and one which would probably make them run quieter as well if you got vibration suppressed as well