Gikfun MQ2 MQ3 MQ4 MQ5 MQ6 MQ7 MQ8 MQ9 MQ135 sensor each 1pc Diy for Arduino EK8238 MQ-2 MQ-3 MQ-4 MQ-5 MQ-6 MQ-7 MQ-8 MQ-9 MQ-135 sensor each 1pc for arduino The sensor need to solder onto board by yourself DIY Kits