Wow, what a brilliant key! At 4.75mm, a snug fit on all my bleed screws. Large physical size of 'wings' give plenty of torque on stiff bleed screws without rounding off the square. I wish that I had had one of these in my toolkit years ago.
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10/6/8pcs Radiator Valve Key Faucet Key Radiator Water Tap Plumbing Bleeder Key Air Vent Central Heating Tool Radiator Bleeding
Aliexpress UK
ENHANCED LEVERAGE: The longer handle design provides extra leverage for effortless turning on this Heatlab radiator airer.
eBay
Radiator Valve Key Faucet Key Radiator Water Tap Plumbing Bleeder Key Air Vent Central Heating Tool Heater Wrench Black Wrench
Aliexpress UK
RADIATOR BLEED KEY - 9 SIZES. RADIATOR PARTS. SQUARE HEAD SIZE. DO TAKE CONSIDERATION FOR THE TAPER AT THE END OF KEY WHEN UNWIDING. (FILE DOWN IF PREFERED).
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1Pcs Key Spanners Radiators Carbon Steel Pagoda Head Valves Key Step Wrench with Square 1/2inch Ratchet Drive Radiators Wrench
Aliexpress UK
ENHANCED LEVERAGE: Longer handle design provides extra leverage for effortless turning on this Heatlab radiator airer. UNBREAKABLE STAINLESS STEEL: Constructed from superior 17-7 heat-treated stainless steel, ensuring strength and durability when radiator bleeding.
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YUANJ 2/5PCS Radiator Exhaust Valve Key Square 5×5mm Radiator Accessories Zinc Alloy Material Socket for Heating Key Tools
Aliexpress UK
Universal Compatibility: Includes 8x4mm, 7x3mm, 7x4mm and 6x6mm to fit most lockshield radiator valves, including Myson Matchmate models.
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Universal Cross Key Control Cabinet Keys 4-Way Multifunctional Key for Water Electricity Meter Radiator Gas Meter
Aliexpress UK
ENHANCED LEVERAGE: Longer handle design provides extra leverage for effortless turning on this Heatlab radiator airer. The Ultimate Radiator Key. UNBREAKABLE STAINLESS STEEL: Constructed from superior 17-7 heat-treated stainless steel, ensuring strength and durability when radiator bleeding.
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Multi Functional Utility Key Wrench Plumbers Key Triangle Cabinet Spanner Key For Radiators Gas Electric Meter Boxes Faucet
Aliexpress UK
2PC CLOCK TYPE RADIATORS KEYS.
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1 pc square radiator step wrench, 1/2 inch universal step wrench, used for pipes and radiator shaped master keys,
Aliexpress UK
Vertical Radiators. Horizontal Radiators. Flat Panel Radiator. Towel Rails. Radiator Valves & Accessories. Can be use on all UK water heating systems(tank fed or combi systems etc.). Central Heating Radiator.
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2pcs Radiator Exhaust Valve Key Square 5×5mm Radiator Accessories Zinc Alloy Material Socket For Standard Heating Valves
Aliexpress UK