Built-in boat cup holders are often too small, too far away, or not shaped for handled tumblers. This adjustable boat cup holder is designed to add a convenient drink spot to suitable vertical rails, grab bars, and pole-style mounting points without drilling. The open-side cradle helps make room for many handled tumblers, while the adjustable cup space supports everyday drink containers such as cans, bottles, and larger travel cups. The white PETG 3D printed body gives the holder a clean look for boating setups and makes the functional shape easy to see. Use it near the console, fishing seat, pontoon seating area, or other secure vertical mounting points where a drink holder is needed. For best results, measure your rail and drink base before purchase, tighten the strap securely after installation, and check the holder before each trip.