Ruddog 5mm Gold Cooling Head Bullet Plugs (10)

Unusably tight - cannot be inserted more than 2/3rds of their length. These measure ~4.95mm at the shank, and all of my batteries (Protek, Reedy, Motiv, Fantom) measure ~5.05mm. 0.1mm clearance is way too tight for this application. Other bullets that fit properly are in the 4.70-4.85mm range.

I'd return these as defective, but I tossed the package. Learn from my mistake and buy a different brand.