Stainless steel ball bearing with a 12 mm bore, carrying the wiper rod in a Trojan ultraviolet reactor. The bearing lets the wiper assembly travel along the quartz sleeves at the low, even drag the drive is designed for; a seized or corroded bearing is a common cause of a wiper that stalls mid-stroke. Stainless steel is specified because the bearing sits in the wetted and chemically aggressive environment of a UV chamber. Trojan part 794244. Contact us if you are unsure whether this part fits your UV system.