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    PR # 32233                                                                   
     The compactness of radio-selected BL Lac objects and their detection        
     in gamma-rays indicate that Compton scattering plays a fundamental          
     role in the physics of these objects. We propose to observe the three       
     X-ray-brightest BL Lacs from a complete radio-selected                      
     PSPC/IPC-observed sample that show evidence of a flat tail above 1-2        
     keV, possibly associated with an emerging Compton component.                
     Characterizing the hard Compton tails will allow us to (1) determine        
     the physical parameters in these sources, (2) distinguish among             
     possible origins for the seed photons, and (3) contrast the high            
     energy properties of radio-selected BL Lacs, poorly studied above           
     2~keV, with the distinct but related class of X-ray-selected BL Lacs,       
    which are well studied and app                                               
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