Manfrotto 501PL / 504PL Video Quick-Release Plate
Direct Answer
The Manfrotto 501PL Video Plate (and its wide 504PL sibling) is the international standard sliding quick-release plate for professional video fluid heads (Manfrotto 502, 504X, Nitrotech, Benro, Sachtler Ace, DJI RS2/RS3/RS4 gimbals). Measuring 50.0 mm wide with a long sliding travel channel, it allows precise center-of-gravity balancing for cinema rigs.
Source: Manfrotto Professional Video Division / DJI Ronin Technical Standards
Specs
| Plate Width (Top Sliding Rail) | 50.0 ± 0.5 mm (1.97 in) |
| Plate Length (501PL) | 86.0 mm (3.39 in) | 501PLONG: 140.0 mm (5.51 in) for heavy telephoto rigs |
| Mounting Studs | Dual captive screws: 1/4"-20 UNC and 3/8"-16 UNC with spring-loaded registration pin |
| Side Laser Scale | Millimeter travel scale (0 to 50 mm) for repeatable gimbal balancing |
| Gimbal Integration | Native quick-release receiver on DJI Ronin RS 2, RS 3 Pro, RS 4 Pro gimbals |
| Fluid Head Standard | Standard receiver on Manfrotto 500, 502, 504, 509 fluid heads, SmallRig video tripods |
Cinema Camera Balancing Channel
Because video rigs change balance points drastically when adding matte boxes, follow focus motors, or heavy telephoto cine primes, the 501PL plate features an $86\text{ mm}$ longitudinal sliding channel. The operator slides the entire camera fore and aft inside the fluid head receiver to balance the tilt axis before locking the clamp.