The MFJ-260C is an air cooled, non-inductive resistor in a perforated metal housing. It has SO-239 connectors. You can handle a full load for 30 seconds. Silk-screened derating curve to 5 minutes. Handles 300 Watts. SWR below 1.1:1 to
30MHz, 1.5:1 from 30 to 650Mhz. It measures a super compact 2-1/4 x 2-1/4 x 7 inches.

Specifications
IMPEDANCE : 50 Ohms, +/- 10%
VSWR : Max: 1.3:1, 0-650MHz
POWER : 300 Watts for 30 seconds
DISSIPATION : (2 min cooldown) 25 Watts continuous
DIMENSIONS : 2-1/4" x 2-1/4" x 7"