$fn=64;

// Parameters
diameter = 250;
height = 25;
wall_thickness = 3;
base_thickness = 3;

// Calculated variables
radius = diameter / 2;
inner_radius = radius - wall_thickness;

difference() {
    // Outer body
    cylinder(r=radius, h=height);
    
    // Inner cutout for water collection
    translate([0, 0, base_thickness])
        cylinder(r=inner_radius, h=height - base_thickness + 1); // +1 prevents Z-fighting
}