Features: - dual valve, closting and latching speed controlled by two separate requlating valves. -universal applicatin: Standard, top-jamb, parallel arm installations. -standard packing no include parallel arm bracket. The bracket be provided upon request. -reionforced type adjustable tube arm. -rack and pinion operation contained in a high tensile precision cast aluminum housing for the highest quality. -high quality hydraulic fluid for high lubricity and constant lubrication. -optional back check (503bc, 504bc, 505bc), controlled by separate regulating value. -finish selection: Silver(alum)