Quality replacement T5 4 pin uv tubes for 11 and 25 watt uv units

T5 4 Pin are the thinner style 4 pins on one end only, approximately 15 mm in diameter .

They have a porcelain effect fitting on each end

Larger the wattage usually the longer they are.

However 6 and 11 watt are the same length and 8 and 16 watt are the same length