Merritt Sentry Drive Side Hub Guard Description: The Merritt Sentry rear hub guard is molded from a durable and fast sliding nylon composite. Designed to work with as many different rear hub and frame combinations as possible, the Sentry guard can work on either the drive side or non-drive side and protects the hub flange and spokes from grind damage. But unlike most guards, the Sentry installs on the outside of the dropout, so there's no hub hardware to replace and it doesn't have any effect on axle spacing. Fits 14mm male and female hubs, and also 3/8" female hubs with the included adapter.