As stated, those are Scotchlocks, UR's (or UY or UG's).
The issue is those don't fit down the standard 3/8" hole and can't be easily taped to allow such. Also, if you overcrimp them, you can cut or nick the cabling. Also, not designed or intended for stranded cabling. Many people overcrimp these, that drives the blade too deep usually nicking the conductor, which in turn negates the reason why you'd use a U connector, which is to have a gastight connection (insulation displacement).