Grease Button Head Coupler, Standard Pull-On, Female 1/8 NPT

Button head couplers like this one connect to button head grease fittings specifically, not the more common zerk style. The female 1/8 NPT thread on this coupler is what connects it to your grease gun hose or equipment on one end, and the pull-on mechanism is what grabs onto the button head fitting on the other. If your machinery uses button head fittings, this is the right coupler for that job.