Omega OBL2 Pro Backstroke Ledge

From Libre Aquatics Wiki, the free aquatics reference

The OBL2 Pro Backstroke Ledge, made by Swiss Timing and sold under its Omega brand, is a backstroke start device: a removable ledge that hooks over the top of an Omega starting platform and gives a backstroke swimmer a non-slip foothold on the wall at the start of a race. The swimmer rotates a spring-assisted mechanism to set the footrest at one of five heights, and after the start an official lifts the whole unit off the block. Swiss Timing states that the OBL2 Pro received FINA approval at the federation’s December 2014 convention in Doha and describes it as the second generation of the device, used at the highest level of competition.¹ It is the ledge model that has been evaluated in independent biomechanical research.²

The device is matched to Swiss Timing’s own starting blocks: the company lists it as fully compatible with the OSB11 and OSB14 blocks and the OSB12 platform, and its mounting assumes the slots of those blocks.¹³ This contrasts with strap-around designs such as the FINIS wedge, which fit a range of generic blocks, and with the self-retracting CTS device; comparisons across the class are covered in the backstroke start devices overview.

Design and components¶

The unit has a lower part that leans against the end wall of the pool and carries the footrest, and an upper part that hooks the assembly over the starting platform. The footrest is molded from polypropylene reinforced with 10% fiberglass and covered with an anti-slip surface; the housings are ABS and the springs and screws are stainless steel. The upper part holds a rotating adjustment mechanism, described by Swiss Timing as patent pending, with a return spring that allows one-handed adjustment, including by a swimmer in the water, and a handlebar for lifting the unit off after the start.³¹

Numbered service parts include the footrest (3454.110), rims (3454.111), left and right supports (3454.120, 3454.121), protection membranes (3454.114, 3454.115), adjustment ring (3454.119), warning label (3454.117), protection cap (3454.118), and safety clasp (3454.116), along with the straps, bars, spring, and locking ring.³

In 2025 Swiss Timing was granted a US patent for a starting block with a backstroke ledge built into the block itself, held on flexible straps with return springs and stowed by an official through a positioning rod. That patent (US 12,465,833, priority 2021) describes an integrated successor design rather than the separate OBL2 Pro unit.⁴

Installation and mounting¶

The ledge installs on the platform top: the block’s own footrest is set to position 3, the fins of the ledge’s supports drop into the top slots of the block, and the unit slides forward to its stop, with the adjustment ring on the right as seen from behind the block.³

Calibration ties the numbered scale to the water level. With the Z scale at 0, four screws on the adjustment ring are loosened (maximum torque 3 Nm when retightening), the straps are wound until the upper edge of the footrest sits at water level, and the ring is fixed again. Swiss Timing notes that a pool’s filtration system raises the water level by about 2 cm, so the setting is made with the pump off, as it normally is during racing. Both straps must run under the rims; routed over them, the unit can unhook under load at the start. A safety clasp on the right rim keeps the strap positioned and is checked before each competition.³

Operation¶

Each swimmer can adjust the footrest before the start, including from the water: pulling the bar sideways unlocks the mechanism, the footrest is rotated to the chosen number on the scale, and the return spring recalls and locks the setting. The standard unit offers five positions in 2 cm steps, from 4 cm below to 4 cm above water level, the range the World Aquatics facilities rule allows; removing a locking screw frees further 2 cm steps, which the manual leaves to the governing rules of the competition.³⁵

The ledge does not retract. After the start, the assigned officials, such as the inspectors of turns, immediately lift the units off the starting blocks, either by the handlebar onto the deck or by folding the footrest behind the block’s own footrest, so the end walls and touchpads are clear for turns and finishes.³¹ The manual also warns against loading the ledge when it is rotated to a 90 degree position.³

Effect on the start¶

The OBL2 is the ledge used in the independent study of backstroke ledge starts: a biomechanical comparison found starts with the ledge reached the 10 m mark about 0.13 s sooner, with less variation and a longer head-entry distance, than starts from the bare wall.² The details of that study, and the history of the equipment class, are covered in the backstroke start devices overview.

Care and maintenance¶

Swiss Timing advises rinsing the unit with fresh water after each use to remove chlorinated water, drying it fully before storage, and periodically checking the stainless steel screws and springs for oxidation, which can appear in aggressive environments such as salt water and is cleaned with soapy water or a mild detergent. The ABS parts are wiped with a damp cloth or chamois; hypochlorite bleach, chloride-containing cleaners, high-proof alcohol, acetone, and other solvents are to be avoided. The unit should not be stored under heavy objects, and after a severe impact or drop it should be checked and not used in case of doubt.³

Specifications¶


Part number	`3454.789`
Size	800 × 150 × 130 mm (L × W × H)
Weight	3.9 kg
Footrest	Polypropylene, 10% fiberglass reinforced, anti-slip surface
Height settings	Five, in 2 cm steps, −4 to +4 cm relative to water level
Adjustment	Rotating mechanism with return spring, one-handed, usable from the water
Retraction	None; removed from the block by an official after the start
Compatibility	Omega OSB11, OSB14 blocks and OSB12 platform
Certification	Described by Swiss Timing as fully FINA-compliant; FINA approval December 2014 (Doha)

References¶

Swiss Timing, OBL2 Pro Backstroke Ledge datasheet (October 2015; reference, dimensions, materials, compliance, and Doha approval). ↩ ↩² ↩³ ↩⁴
Barkwell & Dickey, Backstroke start performance: the impact of using the Omega OBL2 backstroke ledge (Sports Biomechanics, 2018). ↩ ↩²
Swiss Timing, OBL2-PRO Omega Backstroke Ledge User’s Manual (3454.521.02) (linked copy is version 1.1, November 2015; component part numbers follow the revised version 1.4, April 2026). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹
US Patent 12,465,833 B2, Starting block or base plate with a supporting ledge device for a start of a backstroke race (assignee Swiss Timing Ltd; priority 14 October 2021, granted 11 November 2025). ↩
World Aquatics, Facilities Rules 2021–2025, FR 2.1.11 (backstroke ledge). ↩

Last updated July 27, 2026.