Next we have the bit float the most common being the Baker "F" and "G" Both fit inside the bit sub on top of the bit.  The Baker "F" Drill Pipe Float Valve provides a positive and instantaneous shut-off against high or low pressure, assuring continuous control of fluid flow during drilling.   A fast-acting plunger opens when the kelly is pulled out of the hole, then closes, eliminating breakage of a wet joint. The plunger type valve also prevents flow back when adding joints and keeps cuttings out of the drill pipe, preventing bit plugging while making connections. The likelihood of having to pull a wet string with its attendant safety hazards and expensive down time is eliminated. For normal drilling operations, the durable Model "F" is the most economical choice and is available in all sizes.    Type "G" Drill Pipe Float Valves are made of normalized, quenched, and tempered alloy steel to resist wear and erosion.   The flapper valve opens fully during circulation, providing an unrestricted bore through the valve, thereby effectively prolonging the life of the valve and drill collar, as there is no diversion of fluid against the drill collar ID.   When circulation stops, the flapper closes instantly to prevent cuttings from entering the drill string and plugging the bit. The valve opens when the first joint is raised out of the hole assuring the first joints drain and are not pulled wet. This saves mud and avoids safety hazards and down time. The flapper type valve complements primary blowout prevention equipment to provide complete internal pressure control.