Give Your Speakers a New Set of Wheels Speakers are heavy. We move a seemingly endless variety of pro equipment around at Sweetwater on a day-to-day basis, and as light as JBL's SRX900 series of speakers and subwoofers are, our backs are grateful for the Universal Accessory Caster Kit! These durable casters are the perfect upgrade to your SRX900-series product, and they'll make moving and repositioning your live sound setup a breeze.JBL Universal Accessory Caster Kit Features: Designed for JBL's SRX900-series of line array speakers and subwoofers Road-worthy and durable design is ideal for storage and transport 4 casters included