E27 LED Smokey ST64 Filament Bulb 4W 400lm - Cool White 4000K

This is an ST64 filament bulb with a smoke tinted glass envelope and an E27 screw cap. ST64 is the tall teardrop outline, wide at the belly and tapering to a rounded crown, and inside it four LED filament strands sit in a pair of narrow Vs so the lit element reads as clean lines rather than a single coil. It draws 4W, and the pack states 400 lumens, a 40W replacement and a colour temperature of 4000K, which is cool white.

Because the glass is tinted rather than clear, this is a bulb meant to be on show. It suits open pendants, cage fittings, a cluster of bare flexes over a kitchen island, or a run of wall brackets down a hallway, anywhere the lamp is part of the fitting instead of hidden behind a shade. A tinted envelope softens the view of the filaments, which helps at eye level, and the grey cast means the bulb still looks considered when it is switched off. At 4000K the light is neutral and crisp rather than yellow, so it reads well in kitchens, home workshops and utility rooms.

Both the specification and the pack confirm dimming, so the level can come down in the evening; use a dimmer rated for LED loads, ideally a trailing edge type, because older dimmers built for filament halogen can hum or flicker at the bottom of their travel. The pack prints a 15 year lifespan and 15,000 hours, and the energy label gives class F at 4kWh per 1000 hours. Each box holds a single bulb and the minimum order is 12, in multiples of 12. Other LED bulbs from the same maker are on the site in B15 (SBC) candle and GU10 fittings.

Will this fit my existing lamp holder?

It has an E27 screw cap, the larger of the two common screw sizes used in the UK. Check that the old bulb screws in rather than pushing and twisting.

What does 4000K cool white look like in a room?

It is a neutral white with no yellow in it, cleaner in feel than a 2700K warm white and closer to the light you get on an overcast day.

Can I use it on a dimmer switch?

Yes, the specification and the pack both confirm it is dimmable. Fit a dimmer rated for LED loads, as a trailing edge type usually gives the smoothest control.

How bright is 400 lumens in practice?

The pack calls it a 40W replacement, so it suits decorative pendants and wall brackets rather than lighting a whole large room on its own.

How long should it last?

The pack prints a 15 year lifespan and 15,000 hours of use. How long it lasts for you depends on how many hours a day it is switched on.

Will the ST64 shape fit inside a small shade?

The 64 in ST64 is the widest diameter in millimetres, so measure the opening of a shade or a cage before ordering these.