The LPR-90 is excellent tape and the best balance of sound quality, length and cost
LPR-90 has a total coating and base thickness of 1.4mil - 35.5um and is the long play version of the Studio Master tape SM-900
SM-900 has a total coating and base thickness of 2.05mil - 52um so being thicker you get less length on the spool
The SM-900 is the better sounding tape though but not that much in it
Alan
Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, Micro Sieki MA505 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20, Revox A77, B77, PR99, TEAC X1000 & 3440, Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Avondale NCC300 Mono Block, Speakers Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500