Billiard table manufacturers have produced convertible billiard tables (in the broad sense) that double as dining tables or as table tennis, foosball, or air hockey, tables, with removable hard tops. Home pool tables, which often lack a ball-return system, are commonly either 4 × 8 ft or 3.5 × 7 ft models, a medium between 3 × 6 ft. bar/pub tables and 4.5 × 9 ft tournament-size models. Low-end tables tend toward the smaller range, and may have MDF or wood beds as an alternative to slate; those with light-weight beds may be foldable for storage, as with table tennis. Miniature tables
Outer billiard Tabachnikov showed that all orbits are unbounded for a certain class of convex polygons in the hyperbolic plane. The authors call such polygons "large". (See the reference for the definition.) Dogru and Otten then extended this work in 2011 by specifying the conditions under which a regular polygonal table in the hyperbolic plane have all orbits unbounded, that is, are large. In ordinary polygonal billiards, the existence of periodic orbits is a major unsolved problem. For instance, it is unknown if every triangular shaped table has a periodic billiard path. More progress has been made for outer billiards, though the