These replacement ultraviolet 'blacklight' lamps are compatible with Terratek branded bug killers requiring 12 inch 8W ultraviolet lamps. such as insect zappers model Terratek TT16FZ  . They will also work in other brands of fly zapper that take 300mm 8W UV bulbs

Specifications:

• Wattage: 8 Watts
• Bulb length: 30cm / 12 inches
• Weight: 60g
• Average life: 6000 hours
• Cap type:  G5
• Quantity: 4 tubes
• Type: T5
• Compatible part no: 8W T5 BL 365

It is also advisable to replace the starters in your insect killer when replacing the bulbs as your old starters may not be able to provide enough power to reliably light your new lamps. You can find suitable starters here https://www.ebay.co.uk/itm/293129730819